- Type Parameters:
T- the type of the class modeled by thisClassobject. For example, the type ofString.classisClass<String>. UseClass<?>if the class being modeled is unknown.
- All Implemented Interfaces:
Serializable,Constable,TypeDescriptor,TypeDescriptor.OfField<Class<?>>,AnnotatedElement,GenericDeclaration,Type
Class represent classes and
interfaces in a running Java application. An enum class and a record
class are kinds of class; an annotation interface is a kind of
interface. Every array also belongs to a class that is reflected as
a Class object that is shared by all arrays with the same
element type and number of dimensions. The primitive Java types
(boolean, byte, char, short,
int, long, float, and double), and the
keyword void are also represented as Class objects.
Class has no public constructor. Instead a Class
object is constructed automatically by the Java Virtual Machine when
a class is derived from the bytes of a class file through
the invocation of one of the following methods:
-
ClassLoader::defineClass -
java.lang.invoke.MethodHandles.Lookup::defineClass -
java.lang.invoke.MethodHandles.Lookup::defineHiddenClass
The methods of class Class expose many characteristics of a
class or interface. Most characteristics are derived from the class
file that the class loader passed to the Java Virtual Machine or
from the class file passed to Lookup::defineClass
or Lookup::defineHiddenClass.
A few characteristics are determined by the class loading environment
at run time, such as the module returned by getModule().
The following example uses a Class object to print the
class name of an object:
void printClassName(Object obj) {
System.out.println("The class of " + obj +
" is " + obj.getClass().getName());
}
It is also possible to get the Class object for a named
class or interface (or for void) using a class literal.
For example:
System.out.println("The name of class Foo is: "+Foo.class.getName());
Some methods of class Class expose whether the declaration of
a class or interface in Java source code was enclosed within
another declaration. Other methods describe how a class or interface
is situated in a nest. A nest is a set of
classes and interfaces, in the same run-time package, that
allow mutual access to their private members.
The classes and interfaces are known as nestmates.
One nestmate acts as the
nest host, and enumerates the other nestmates which
belong to the nest; each of them in turn records it as the nest host.
The classes and interfaces which belong to a nest, including its host, are
determined when
class files are generated, for example, a Java compiler
will typically record a top-level class as the host of a nest where the
other members are the classes and interfaces whose declarations are
enclosed within the top-level class declaration.
A class or interface created by the invocation of
Lookup::defineHiddenClass is a hidden
class or interface.
All kinds of class, including enum classes and record classes, may be
hidden classes; all kinds of interface, including annotation interfaces,
may be hidden interfaces.
The name of a hidden class or interface is
not a binary name,
which means the following:
- A hidden class or interface cannot be referenced by the constant pools of other classes and interfaces.
- A hidden class or interface cannot be described in
nominal form by
Class::describeConstable,ClassDesc::of, orClassDesc::ofDescriptor. - A hidden class or interface cannot be discovered by
Class::forNameorClassLoader::loadClass.
Class.- See Java Language Specification:
-
15.8.2 Class Literals
- Since:
- 1.0
- See Also:
-
Nested Class Summary
Nested classes/interfaces declared in interface java.lang.invoke.TypeDescriptor
TypeDescriptor.OfField<F extends TypeDescriptor.OfField<F>>, TypeDescriptor.OfMethod<F extends TypeDescriptor.OfField<F>,M extends TypeDescriptor.OfMethod<F, M>> -
Method Summary
Modifier and TypeMethodDescriptionClass<?>Returns aClassfor an array type whose component type is described by this Class.<U> Class<? extends U>asSubclass(Class<U> clazz) Casts thisClassobject to represent a subclass of the class represented by the specified class object.Casts an object to the class or interface represented by thisClassobject.Class<?>Returns the component type of thisClass, if it describes an array type, ornullotherwise.Returns a nominal descriptor for this instance, if one can be constructed, or an emptyOptionalif one cannot be.Returns the descriptor string of the entity (class, interface, array class, primitive type, orvoid) represented by thisClassobject.booleanReturns the assertion status that would be assigned to this class if it were to be initialized at the time this method is invoked.static Class<?>Returns theClasswith the given binary name in the given module.static Class<?>Returns theClassobject associated with the class or interface with the given string name.static Class<?>forName(String name, boolean initialize, ClassLoader loader) Returns theClassobject associated with the class or interface with the given string name, using the given class loader.Returns an array ofAnnotatedTypeobjects that represent the use of types to specify superinterfaces of the entity represented by thisClassobject.Returns anAnnotatedTypeobject that represents the use of a type to specify the superclass of the entity represented by thisClassobject.<A extends Annotation>
AgetAnnotation(Class<A> annotationClass) Returns this element's annotation for the specified type if such an annotation is present, else null.Returns annotations that are present on this element.<A extends Annotation>
A[]getAnnotationsByType(Class<A> annotationClass) Returns annotations that are associated with this element.Returns the canonical name of the underlying class as defined by The Java Language Specification.Class<?>[]Returns an array containingClassobjects representing all the public classes and interfaces that are members of the class represented by thisClassobject.Returns the class loader for the class.Class<?>Returns theClassrepresenting the component type of an array.getConstructor(Class<?>... parameterTypes) Returns aConstructorobject that reflects the specified public constructor of the class represented by thisClassobject.Constructor<?>[]Returns an array containingConstructorobjects reflecting all the public constructors of the class represented by thisClassobject.<A extends Annotation>
AgetDeclaredAnnotation(Class<A> annotationClass) Returns this element's annotation for the specified type if such an annotation is directly present, else null.Returns annotations that are directly present on this element.<A extends Annotation>
A[]getDeclaredAnnotationsByType(Class<A> annotationClass) Returns this element's annotation(s) for the specified type if such annotations are either directly present or indirectly present.Class<?>[]Returns an array ofClassobjects reflecting all the classes and interfaces declared as members of the class represented by thisClassobject.getDeclaredConstructor(Class<?>... parameterTypes) Returns aConstructorobject that reflects the specified constructor of the class or interface represented by thisClassobject.Constructor<?>[]Returns an array ofConstructorobjects reflecting all the constructors declared by the class represented by thisClassobject.getDeclaredField(String name) Returns aFieldobject that reflects the specified declared field of the class or interface represented by thisClassobject.Field[]Returns an array ofFieldobjects reflecting all the fields declared by the class or interface represented by thisClassobject.getDeclaredMethod(String name, Class<?>... parameterTypes) Returns aMethodobject that reflects the specified declared method of the class or interface represented by thisClassobject.Method[]Returns an array containingMethodobjects reflecting all the declared methods of the class or interface represented by thisClassobject, including public, protected, default (package) access, and private methods, but excluding inherited methods.Class<?>If the class or interface represented by thisClassobject is a member of another class, returns theClassobject representing the class in which it was declared.Class<?>Returns the immediately enclosing class of the underlying class.Constructor<?>If thisClassobject represents a local or anonymous class within a constructor, returns aConstructorobject representing the immediately enclosing constructor of the underlying class.If thisClassobject represents a local or anonymous class within a method, returns aMethodobject representing the immediately enclosing method of the underlying class.T[]Returns the elements of this enum class or null if this Class object does not represent an enum class.Returns aFieldobject that reflects the specified public member field of the class or interface represented by thisClassobject.Field[]Returns an array containingFieldobjects reflecting all the accessible public fields of the class or interface represented by thisClassobject.Type[]Returns theTypes representing the interfaces directly implemented by the class or interface represented by thisClassobject.Returns theTyperepresenting the direct superclass of the entity (class, interface, primitive type or void) represented by thisClassobject.Class<?>[]Returns the interfaces directly implemented by the class or interface represented by thisClassobject.Returns aMethodobject that reflects the specified public member method of the class or interface represented by thisClassobject.Method[]Returns an array containingMethodobjects reflecting all the public methods of the class or interface represented by thisClassobject, including those declared by the class or interface and those inherited from superclasses and superinterfaces.intReturns the Java language modifiers for this class or interface, encoded in an integer.Returns the module that this class or interface is a member of.getName()Returns the name of the entity (class, interface, array class, primitive type, or void) represented by thisClassobject.Class<?>Returns the nest host of the nest to which the class or interface represented by thisClassobject belongs.Class<?>[]Returns an array containingClassobjects representing all the classes and interfaces that are members of the nest to which the class or interface represented by thisClassobject belongs.Gets the package of this class.Returns the fully qualified package name.Class<?>[]Returns an array containingClassobjects representing the direct subinterfaces or subclasses permitted to extend or implement this class or interface if it is sealed.Returns theProtectionDomainof this class.Returns an array ofRecordComponentobjects representing all the record components of this record class, ornullif this class is not a record class.getResource(String name) Finds a resource with a given name.getResourceAsStream(String name) Finds a resource with a given name.Object[]Gets the signers of this class.Returns the simple name of the underlying class as given in the source code.Returns theClassrepresenting the direct superclass of the entity (class, interface, primitive type or void) represented by thisClass.Return an informative string for the name of this class or interface.TypeVariable<Class<T>>[]Returns an array ofTypeVariableobjects that represent the type variables declared by the generic declaration represented by thisGenericDeclarationobject, in declaration order.booleanReturns true if thisClassobject represents an annotation interface.booleanisAnnotationPresent(Class<? extends Annotation> annotationClass) Returns true if an annotation for the specified type is present on this element, else false.booleanReturnstrueif and only if the underlying class is an anonymous class.booleanisArray()Determines if thisClassobject represents an array class.booleanisAssignableFrom(Class<?> cls) Determines if the class or interface represented by thisClassobject is either the same as, or is a superclass or superinterface of, the class or interface represented by the specifiedClassparameter.booleanisEnum()Returns true if and only if this class was declared as an enum in the source code.booleanisHidden()Returnstrueif and only if the underlying class is a hidden class.booleanisInstance(Object obj) Determines if the specifiedObjectis assignment-compatible with the object represented by thisClass.booleanDetermines if thisClassobject represents an interface type.booleanReturnstrueif and only if the underlying class is a local class.booleanReturnstrueif and only if the underlying class is a member class.booleanisNestmateOf(Class<?> c) Determines if the givenClassis a nestmate of the class or interface represented by thisClassobject.booleanDetermines if the specifiedClassobject represents a primitive type.booleanisRecord()Returnstrueif and only if this class is a record class.booleanisSealed()Returnstrueif and only if thisClassobject represents a sealed class or interface.booleanReturnstrueif and only if this class has the synthetic modifier bit set.Deprecated.This method propagates any exception thrown by the nullary constructor, including a checked exception.Returns a string describing thisClass, including information about modifiers and type parameters.toString()Converts the object to a string.
-
Method Details
-
toString
Converts the object to a string. The string representation is the string "class" or "interface", followed by a space, and then by the name of the class in the format returned bygetName. If thisClassobject represents a primitive type, this method returns the name of the primitive type. If thisClassobject represents void this method returns "void". If thisClassobject represents an array type, this method returns "class " followed bygetName. -
toGenericString
Returns a string describing thisClass, including information about modifiers and type parameters. The string is formatted as a list of type modifiers, if any, followed by the kind of type (empty string for primitive types andclass,enum,interface,@interface, orrecordas appropriate), followed by the type's name, followed by an angle-bracketed comma-separated list of the type's type parameters, if any, including informative bounds on the type parameters, if any. A space is used to separate modifiers from one another and to separate any modifiers from the kind of type. The modifiers occur in canonical order. If there are no type parameters, the type parameter list is elided. For an array type, the string starts with the type name, followed by an angle-bracketed comma-separated list of the type's type parameters, if any, followed by a sequence of[]characters, one set of brackets per dimension of the array.Note that since information about the runtime representation of a type is being generated, modifiers not present on the originating source code or illegal on the originating source code may be present.
- Returns:
- a string describing this
Class, including information about modifiers and type parameters - Since:
- 1.8
-
forName
Returns theClassobject associated with the class or interface with the given string name. Invoking this method is equivalent to:
whereClass.forName(className, true, currentLoader)currentLoaderdenotes the defining class loader of the current class.For example, the following code fragment returns the runtime
Classdescriptor for the class namedjava.lang.Thread:Class t = Class.forName("java.lang.Thread")A call to
forName("X")causes the class namedXto be initialized.- Parameters:
className- the fully qualified name of the desired class.- Returns:
- the
Classobject for the class with the specified name. - Throws:
LinkageError- if the linkage failsExceptionInInitializerError- if the initialization provoked by this method failsClassNotFoundException- if the class cannot be located- See Java Language Specification:
-
12.2 Loading of Classes and Interfaces
12.3 Linking of Classes and Interfaces
12.4 Initialization of Classes and Interfaces
-
forName
public static Class<?> forName(String name, boolean initialize, ClassLoader loader) throws ClassNotFoundException Returns theClassobject associated with the class or interface with the given string name, using the given class loader. Given the fully qualified name for a class or interface (in the same format returned bygetName) this method attempts to locate and load the class or interface. The specified class loader is used to load the class or interface. If the parameterloaderis null, the class is loaded through the bootstrap class loader. The class is initialized only if theinitializeparameter istrueand if it has not been initialized earlier.If
namedenotes a primitive type or void, an attempt will be made to locate a user-defined class in the unnamed package whose name isname. Therefore, this method cannot be used to obtain any of theClassobjects representing primitive types or void.If
namedenotes an array class, the component type of the array class is loaded but not initialized.For example, in an instance method the expression:
is equivalent to:Class.forName("Foo")
Note that this method throws errors related to loading, linking or initializing as specified in Sections 12.2, 12.3, and 12.4 of The Java Language Specification. Note that this method does not check whether the requested class is accessible to its caller.Class.forName("Foo", true, this.getClass().getClassLoader())- Parameters:
name- fully qualified name of the desired classinitialize- iftruethe class will be initialized (which implies linking). See Section 12.4 of The Java Language Specification.loader- class loader from which the class must be loaded- Returns:
- class object representing the desired class
- Throws:
LinkageError- if the linkage failsExceptionInInitializerError- if the initialization provoked by this method failsClassNotFoundException- if the class cannot be located by the specified class loaderSecurityException- if a security manager is present, and theloaderisnull, and the caller's class loader is notnull, and the caller does not have theRuntimePermission("getClassLoader")- See Java Language Specification:
-
12.2 Loading of Classes and Interfaces
12.3 Linking of Classes and Interfaces
12.4 Initialization of Classes and Interfaces - Since:
- 1.2
- See Also:
-
forName
Returns theClasswith the given binary name in the given module.This method attempts to locate and load the class or interface. It does not link the class, and does not run the class initializer. If the class is not found, this method returns
null.If the class loader of the given module defines other modules and the given name is a class defined in a different module, this method returns
nullafter the class is loaded.This method does not check whether the requested class is accessible to its caller.
- API Note:
- This method returns
nullon failure rather than throwing aClassNotFoundException, as is done by theforName(String, boolean, ClassLoader)method. The security check is a stack-based permission check if the caller loads a class in another module. - Parameters:
module- A modulename- The binary name of the class- Returns:
Classobject of the given name defined in the given module;nullif not found.- Throws:
NullPointerException- if the given module or name isnullLinkageError- if the linkage failsSecurityException-- if the caller is not the specified module and
RuntimePermission("getClassLoader")permission is denied; or - access to the module content is denied. For example,
permission check will be performed when a class loader calls
ModuleReader.open(String)to read the bytes of a class file in a module.
- if the caller is not the specified module and
- See Java Language Specification:
-
12.2 Loading of Classes and Interfaces
12.3 Linking of Classes and Interfaces - Since:
- 9
-
newInstance
Deprecated.This method propagates any exception thrown by the nullary constructor, including a checked exception. Use of this method effectively bypasses the compile-time exception checking that would otherwise be performed by the compiler. TheConstructor.newInstancemethod avoids this problem by wrapping any exception thrown by the constructor in a (checked)InvocationTargetException.The call
can be replaced byclazz.newInstance()
The latter sequence of calls is inferred to be able to throw the additional exception typesclazz.getDeclaredConstructor().newInstance()InvocationTargetExceptionandNoSuchMethodException. Both of these exception types are subclasses ofReflectiveOperationException.Creates a new instance of the class represented by thisClassobject. The class is instantiated as if by anewexpression with an empty argument list. The class is initialized if it has not already been initialized.- Returns:
- a newly allocated instance of the class represented by this object.
- Throws:
IllegalAccessException- if the class or its nullary constructor is not accessible.InstantiationException- if thisClassrepresents an abstract class, an interface, an array class, a primitive type, or void; or if the class has no nullary constructor; or if the instantiation fails for some other reason.ExceptionInInitializerError- if the initialization provoked by this method fails.SecurityException- If a security manager, s, is present and the caller's class loader is not the same as or an ancestor of the class loader for the current class and invocation ofs.checkPackageAccess()denies access to the package of this class.
-
isInstance
Determines if the specifiedObjectis assignment-compatible with the object represented by thisClass. This method is the dynamic equivalent of the Java languageinstanceofoperator. The method returnstrueif the specifiedObjectargument is non-null and can be cast to the reference type represented by thisClassobject without raising aClassCastException.It returnsfalseotherwise.Specifically, if this
Classobject represents a declared class, this method returnstrueif the specifiedObjectargument is an instance of the represented class (or of any of its subclasses); it returnsfalseotherwise. If thisClassobject represents an array class, this method returnstrueif the specifiedObjectargument can be converted to an object of the array class by an identity conversion or by a widening reference conversion; it returnsfalseotherwise. If thisClassobject represents an interface, this method returnstrueif the class or any superclass of the specifiedObjectargument implements this interface; it returnsfalseotherwise. If thisClassobject represents a primitive type, this method returnsfalse.- Parameters:
obj- the object to check- Returns:
- true if
objis an instance of this class - Since:
- 1.1
-
isAssignableFrom
Determines if the class or interface represented by thisClassobject is either the same as, or is a superclass or superinterface of, the class or interface represented by the specifiedClassparameter. It returnstrueif so; otherwise it returnsfalse. If thisClassobject represents a primitive type, this method returnstrueif the specifiedClassparameter is exactly thisClassobject; otherwise it returnsfalse.Specifically, this method tests whether the type represented by the specified
Classparameter can be converted to the type represented by thisClassobject via an identity conversion or via a widening reference conversion. See The Java Language Specification, sections 5.1.1 and 5.1.4, for details.- Parameters:
cls- theClassobject to be checked- Returns:
- the
booleanvalue indicating whether objects of the typeclscan be assigned to objects of this class - Throws:
NullPointerException- if the specified Class parameter is null.- Since:
- 1.1
-
isInterface
public boolean isInterface()Determines if thisClassobject represents an interface type.- Returns:
trueif thisClassobject represents an interface;falseotherwise.
-
isArray
public boolean isArray()Determines if thisClassobject represents an array class.- Specified by:
isArrayin interfaceTypeDescriptor.OfField<T>- Returns:
trueif thisClassobject represents an array class;falseotherwise.- Since:
- 1.1
-
isPrimitive
public boolean isPrimitive()Determines if the specifiedClassobject represents a primitive type.There are nine predefined
Classobjects to represent the eight primitive types and void. These are created by the Java Virtual Machine, and have the same names as the primitive types that they represent, namelyboolean,byte,char,short,int,long,float, anddouble.These objects may only be accessed via the following public static final variables, and are the only
Classobjects for which this method returnstrue.- Specified by:
isPrimitivein interfaceTypeDescriptor.OfField<T>- Returns:
- true if and only if this class represents a primitive type
- Since:
- 1.1
- See Also:
-
isAnnotation
public boolean isAnnotation()Returns true if thisClassobject represents an annotation interface. Note that if this method returns true,isInterface()would also return true, as all annotation interfaces are also interfaces.- Returns:
trueif thisClassobject represents an annotation interface;falseotherwise- Since:
- 1.5
-
isSynthetic
public boolean isSynthetic()Returnstrueif and only if this class has the synthetic modifier bit set.- Returns:
trueif and only if this class has the synthetic modifier bit set- See Java Language Specification:
-
13.1 The Form of a Binary
- See Java Virtual Machine Specification:
-
4.1 The
ClassFileStructure - Since:
- 1.5
- See Also:
-
getName
Returns the name of the entity (class, interface, array class, primitive type, or void) represented by thisClassobject.If this
Classobject represents a class or interface, not an array class, then:- If the class or interface is not hidden, then the binary name of the class or interface is returned.
- If the class or interface is hidden, then the result is a string
of the form:
N + '/' + <suffix>whereNis the binary name indicated by theclassfile passed toLookup::defineHiddenClass, and<suffix>is an unqualified name.
If this
Classobject represents an array class, then the result is a string consisting of one or more '[' characters representing the depth of the array nesting, followed by the element type as encoded using the following table:Element Type Encoding booleanZbyteBcharCclass or interface with binary name N LN;doubleDfloatFintIlongJshortSIf this
Classobject represents a primitive type orvoid, then the result is a string with the same spelling as the Java language keyword which corresponds to the primitive type orvoid.Examples:
String.class.getName() returns "java.lang.String" byte.class.getName() returns "byte" (new Object[3]).getClass().getName() returns "[Ljava.lang.Object;" (new int[3][4][5][6][7][8][9]).getClass().getName() returns "[[[[[[[I"- Returns:
- the name of the class, interface, or other entity
represented by this
Classobject. - See Java Language Specification:
-
13.1 The Form of a Binary
-
getClassLoader
Returns the class loader for the class. Some implementations may use null to represent the bootstrap class loader. This method will return null in such implementations if this class was loaded by the bootstrap class loader.If this
Classobject represents a primitive type or void, null is returned.- Returns:
- the class loader that loaded the class or interface
represented by this
Classobject. - Throws:
SecurityException- if a security manager is present, and the caller's class loader is notnulland is not the same as or an ancestor of the class loader for the class whose class loader is requested, and the caller does not have theRuntimePermission("getClassLoader")- See Also:
-
getModule
Returns the module that this class or interface is a member of. If this class represents an array type then this method returns theModulefor the element type. If this class represents a primitive type or void, then theModuleobject for thejava.basemodule is returned. If this class is in an unnamed module then the unnamedModuleof the class loader for this class is returned.- Returns:
- the module that this class or interface is a member of
- Since:
- 9
-
getTypeParameters
Returns an array ofTypeVariableobjects that represent the type variables declared by the generic declaration represented by thisGenericDeclarationobject, in declaration order. Returns an array of length 0 if the underlying generic declaration declares no type variables.- Specified by:
getTypeParametersin interfaceGenericDeclaration- Returns:
- an array of
TypeVariableobjects that represent the type variables declared by this generic declaration - Throws:
GenericSignatureFormatError- if the generic signature of this generic declaration does not conform to the format specified in section 4.7.9 of The Java Virtual Machine Specification- Since:
- 1.5
-
getSuperclass
Returns theClassrepresenting the direct superclass of the entity (class, interface, primitive type or void) represented by thisClass. If thisClassrepresents either theObjectclass, an interface, a primitive type, or void, then null is returned. If thisClassobject represents an array class then theClassobject representing theObjectclass is returned.- Returns:
- the direct superclass of the class represented by this
Classobject
-
getGenericSuperclass
Returns theTyperepresenting the direct superclass of the entity (class, interface, primitive type or void) represented by thisClassobject.If the superclass is a parameterized type, the
Typeobject returned must accurately reflect the actual type arguments used in the source code. The parameterized type representing the superclass is created if it had not been created before. See the declaration ofParameterizedTypefor the semantics of the creation process for parameterized types. If thisClassobject represents either theObjectclass, an interface, a primitive type, or void, then null is returned. If thisClassobject represents an array class then theClassobject representing theObjectclass is returned.- Returns:
- the direct superclass of the class represented by this
Classobject - Throws:
GenericSignatureFormatError- if the generic class signature does not conform to the format specified in section 4.7.9 of The Java Virtual Machine SpecificationTypeNotPresentException- if the generic superclass refers to a non-existent type declarationMalformedParameterizedTypeException- if the generic superclass refers to a parameterized type that cannot be instantiated for any reason- Since:
- 1.5
-
getPackage
Gets the package of this class.If this class represents an array type, a primitive type or void, this method returns
null.- Returns:
- the package of this class.
-
getPackageName
Returns the fully qualified package name.If this class is a top level class, then this method returns the fully qualified name of the package that the class is a member of, or the empty string if the class is in an unnamed package.
If this class is a member class, then this method is equivalent to invoking
getPackageName()on the enclosing class.If this class is a local class or an anonymous class, then this method is equivalent to invoking
getPackageName()on the declaring class of the enclosing method or enclosing constructor.If this class represents an array type then this method returns the package name of the element type. If this class represents a primitive type or void then the package name "
java.lang" is returned.- Returns:
- the fully qualified package name
- See Java Language Specification:
-
6.7 Fully Qualified Names
- Since:
- 9
-
getInterfaces
Returns the interfaces directly implemented by the class or interface represented by thisClassobject.If this
Classobject represents a class, the return value is an array containing objects representing all interfaces directly implemented by the class. The order of the interface objects in the array corresponds to the order of the interface names in theimplementsclause of the declaration of the class represented by thisClassobject. For example, given the declaration:
suppose the value ofclass Shimmer implements FloorWax, DessertTopping { ... }sis an instance ofShimmer; the value of the expression:
is thes.getClass().getInterfaces()[0]Classobject that represents interfaceFloorWax; and the value of:
is thes.getClass().getInterfaces()[1]Classobject that represents interfaceDessertTopping.If this
Classobject represents an interface, the array contains objects representing all interfaces directly extended by the interface. The order of the interface objects in the array corresponds to the order of the interface names in theextendsclause of the declaration of the interface represented by thisClassobject.If this
Classobject represents a class or interface that implements no interfaces, the method returns an array of length 0.If this
Classobject represents a primitive type or void, the method returns an array of length 0.If this
Classobject represents an array type, the interfacesCloneableandjava.io.Serializableare returned in that order.- Returns:
- an array of interfaces directly implemented by this class
-
getGenericInterfaces
Returns theTypes representing the interfaces directly implemented by the class or interface represented by thisClassobject.If a superinterface is a parameterized type, the
Typeobject returned for it must accurately reflect the actual type arguments used in the source code. The parameterized type representing each superinterface is created if it had not been created before. See the declaration ofParameterizedTypefor the semantics of the creation process for parameterized types.If this
Classobject represents a class, the return value is an array containing objects representing all interfaces directly implemented by the class. The order of the interface objects in the array corresponds to the order of the interface names in theimplementsclause of the declaration of the class represented by thisClassobject.If this
Classobject represents an interface, the array contains objects representing all interfaces directly extended by the interface. The order of the interface objects in the array corresponds to the order of the interface names in theextendsclause of the declaration of the interface represented by thisClassobject.If this
Classobject represents a class or interface that implements no interfaces, the method returns an array of length 0.If this
Classobject represents a primitive type or void, the method returns an array of length 0.If this
Classobject represents an array type, the interfacesCloneableandjava.io.Serializableare returned in that order.- Returns:
- an array of interfaces directly implemented by this class
- Throws:
GenericSignatureFormatError- if the generic class signature does not conform to the format specified in section 4.7.9 of The Java Virtual Machine SpecificationTypeNotPresentException- if any of the generic superinterfaces refers to a non-existent type declarationMalformedParameterizedTypeException- if any of the generic superinterfaces refer to a parameterized type that cannot be instantiated for any reason- Since:
- 1.5
-
getComponentType
Returns theClassrepresenting the component type of an array. If this class does not represent an array class this method returns null.- Returns:
- the
Classrepresenting the component type of this class if this class is an array - Since:
- 1.1
- See Also:
-
getModifiers
public int getModifiers()Returns the Java language modifiers for this class or interface, encoded in an integer. The modifiers consist of the Java Virtual Machine's constants forpublic,protected,private,final,static,abstractandinterface; they should be decoded using the methods of classModifier.If the underlying class is an array class, then its
public,privateandprotectedmodifiers are the same as those of its component type. If thisClassobject represents a primitive type or void, itspublicmodifier is alwaystrue, and itsprotectedandprivatemodifiers are alwaysfalse. If thisClassobject represents an array class, a primitive type or void, then itsfinalmodifier is alwaystrueand its interface modifier is alwaysfalse. The values of its other modifiers are not determined by this specification.The modifier encodings are defined in section 4.1 of The Java Virtual Machine Specification.
- Returns:
- the
intrepresenting the modifiers for this class - See Java Language Specification:
-
8.1.1 Class Modifiers
9.1.1. Interface Modifiers - Since:
- 1.1
- See Also:
-
getSigners
Gets the signers of this class.- Returns:
- the signers of this class, or null if there are no signers. In
particular, this method returns null if this
Classobject represents a primitive type or void. - Since:
- 1.1
-
getEnclosingMethod
If thisClassobject represents a local or anonymous class within a method, returns aMethodobject representing the immediately enclosing method of the underlying class. Returnsnullotherwise. In particular, this method returnsnullif the underlying class is a local or anonymous class immediately enclosed by a class or interface declaration, instance initializer or static initializer.- Returns:
- the immediately enclosing method of the underlying class, if
that class is a local or anonymous class; otherwise
null. - Throws:
SecurityException- If a security manager, s, is present and any of the following conditions is met:- the caller's class loader is not the same as the
class loader of the enclosing class and invocation of
s.checkPermissionmethod withRuntimePermission("accessDeclaredMembers")denies access to the methods within the enclosing class - the caller's class loader is not the same as or an
ancestor of the class loader for the enclosing class and
invocation of
s.checkPackageAccess()denies access to the package of the enclosing class
- the caller's class loader is not the same as the
class loader of the enclosing class and invocation of
- Since:
- 1.5
-
getEnclosingConstructor
If thisClassobject represents a local or anonymous class within a constructor, returns aConstructorobject representing the immediately enclosing constructor of the underlying class. Returnsnullotherwise. In particular, this method returnsnullif the underlying class is a local or anonymous class immediately enclosed by a class or interface declaration, instance initializer or static initializer.- Returns:
- the immediately enclosing constructor of the underlying class, if
that class is a local or anonymous class; otherwise
null. - Throws:
SecurityException- If a security manager, s, is present and any of the following conditions is met:- the caller's class loader is not the same as the
class loader of the enclosing class and invocation of
s.checkPermissionmethod withRuntimePermission("accessDeclaredMembers")denies access to the constructors within the enclosing class - the caller's class loader is not the same as or an
ancestor of the class loader for the enclosing class and
invocation of
s.checkPackageAccess()denies access to the package of the enclosing class
- the caller's class loader is not the same as the
class loader of the enclosing class and invocation of
- Since:
- 1.5
-
getDeclaringClass
If the class or interface represented by thisClassobject is a member of another class, returns theClassobject representing the class in which it was declared. This method returns null if this class or interface is not a member of any other class. If thisClassobject represents an array class, a primitive type, or void,then this method returns null.- Returns:
- the declaring class for this class
- Throws:
SecurityException- If a security manager, s, is present and the caller's class loader is not the same as or an ancestor of the class loader for the declaring class and invocation ofs.checkPackageAccess()denies access to the package of the declaring class- Since:
- 1.1
-
getEnclosingClass
Returns the immediately enclosing class of the underlying class. If the underlying class is a top level class this method returnsnull.- Returns:
- the immediately enclosing class of the underlying class
- Throws:
SecurityException- If a security manager, s, is present and the caller's class loader is not the same as or an ancestor of the class loader for the enclosing class and invocation ofs.checkPackageAccess()denies access to the package of the enclosing class- Since:
- 1.5
-
getSimpleName
Returns the simple name of the underlying class as given in the source code. An empty string is returned if the underlying class is anonymous. A synthetic class, one not present in source code, can have a non-empty name including special characters, such as "$".The simple name of an array class is the simple name of the component type with "[]" appended. In particular the simple name of an array class whose component type is anonymous is "[]".
- Returns:
- the simple name of the underlying class
- Since:
- 1.5
-
getTypeName
Return an informative string for the name of this class or interface.- Specified by:
getTypeNamein interfaceType- Returns:
- an informative string for the name of this class or interface
- Since:
- 1.8
-
getCanonicalName
Returns the canonical name of the underlying class as defined by The Java Language Specification. Returnsnullif the underlying class does not have a canonical name. Classes without canonical names include:- a local class
- a anonymous class
- a hidden class
- an array whose component type does not have a canonical name
- Returns:
- the canonical name of the underlying class if it exists, and
nullotherwise. - Since:
- 1.5
-
isAnonymousClass
public boolean isAnonymousClass()Returnstrueif and only if the underlying class is an anonymous class.- API Note:
- An anonymous class is not a hidden class.
- Returns:
trueif and only if this class is an anonymous class.- See Java Language Specification:
-
15.9.5 Anonymous Class Declarations
- Since:
- 1.5
-
isLocalClass
public boolean isLocalClass()Returnstrueif and only if the underlying class is a local class.- Returns:
trueif and only if this class is a local class.- See Java Language Specification:
-
14.3 Local Class Declarations
- Since:
- 1.5
-
isMemberClass
public boolean isMemberClass()Returnstrueif and only if the underlying class is a member class.- Returns:
trueif and only if this class is a member class.- See Java Language Specification:
-
8.5 Member Type Declarations
- Since:
- 1.5
-
getClasses
Returns an array containingClassobjects representing all the public classes and interfaces that are members of the class represented by thisClassobject. This includes public class and interface members inherited from superclasses and public class and interface members declared by the class. This method returns an array of length 0 if thisClassobject has no public member classes or interfaces. This method also returns an array of length 0 if thisClassobject represents a primitive type, an array class, or void.- Returns:
- the array of
Classobjects representing the public members of this class - Throws:
SecurityException- If a security manager, s, is present and the caller's class loader is not the same as or an ancestor of the class loader for the current class and invocation ofs.checkPackageAccess()denies access to the package of this class.- Since:
- 1.1
-
getFields
Returns an array containingFieldobjects reflecting all the accessible public fields of the class or interface represented by thisClassobject.If this
Classobject represents a class or interface with no accessible public fields, then this method returns an array of length 0.If this
Classobject represents a class, then this method returns the public fields of the class and of all its superclasses and superinterfaces.If this
Classobject represents an interface, then this method returns the fields of the interface and of all its superinterfaces.If this
Classobject represents an array type, a primitive type, or void, then this method returns an array of length 0.The elements in the returned array are not sorted and are not in any particular order.
- Returns:
- the array of
Fieldobjects representing the public fields - Throws:
SecurityException- If a security manager, s, is present and the caller's class loader is not the same as or an ancestor of the class loader for the current class and invocation ofs.checkPackageAccess()denies access to the package of this class.- See Java Language Specification:
-
8.2 Class Members
8.3 Field Declarations - Since:
- 1.1
-
getMethods
Returns an array containingMethodobjects reflecting all the public methods of the class or interface represented by thisClassobject, including those declared by the class or interface and those inherited from superclasses and superinterfaces.If this
Classobject represents an array type, then the returned array has aMethodobject for each of the public methods inherited by the array type fromObject. It does not contain aMethodobject forclone().If this
Classobject represents an interface then the returned array does not contain any implicitly declared methods fromObject. Therefore, if no methods are explicitly declared in this interface or any of its superinterfaces then the returned array has length 0. (Note that aClassobject which represents a class always has public methods, inherited fromObject.)The returned array never contains methods with names "
<init>" or "<clinit>".The elements in the returned array are not sorted and are not in any particular order.
Generally, the result is computed as with the following 4 step algorithm. Let C be the class or interface represented by this
Classobject:- A union of methods is composed of:
- C's declared public instance and static methods as returned by
getDeclaredMethods()and filtered to include only public methods. - If C is a class other than
Object, then include the result of invoking this algorithm recursively on the superclass of C. - Include the results of invoking this algorithm recursively on all direct superinterfaces of C, but include only instance methods.
- C's declared public instance and static methods as returned by
- Union from step 1 is partitioned into subsets of methods with same signature (name, parameter types) and return type.
- Within each such subset only the most specific methods are selected.
Let method M be a method from a set of methods with same signature
and return type. M is most specific if there is no such method
N != M from the same set, such that N is more specific than M.
N is more specific than M if:
- N is declared by a class and M is declared by an interface; or
- N and M are both declared by classes or both by interfaces and N's declaring type is the same as or a subtype of M's declaring type (clearly, if M's and N's declaring types are the same type, then M and N are the same method).
- The result of this algorithm is the union of all selected methods from step 3.
- API Note:
- There may be more than one method with a particular name and parameter types in a class because while the Java language forbids a class to declare multiple methods with the same signature but different return types, the Java virtual machine does not. This increased flexibility in the virtual machine can be used to implement various language features. For example, covariant returns can be implemented with bridge methods; the bridge method and the overriding method would have the same signature but different return types.
- Returns:
- the array of
Methodobjects representing the public methods of this class - Throws:
SecurityException- If a security manager, s, is present and the caller's class loader is not the same as or an ancestor of the class loader for the current class and invocation ofs.checkPackageAccess()denies access to the package of this class.- See Java Language Specification:
-
8.2 Class Members
8.4 Method Declarations - Since:
- 1.1
- A union of methods is composed of:
-
getConstructors
Returns an array containingConstructorobjects reflecting all the public constructors of the class represented by thisClassobject. An array of length 0 is returned if the class has no public constructors, or if the class is an array class, or if the class reflects a primitive type or void.- API Note:
- While this method returns an array of
Constructor<T>objects (that is an array of constructors from this class), the return type of this method isConstructor<?>[]and notConstructor<T>[]as might be expected. This less informative return type is necessary since after being returned from this method, the array could be modified to holdConstructorobjects for different classes, which would violate the type guarantees ofConstructor<T>[]. - Returns:
- the array of
Constructorobjects representing the public constructors of this class - Throws:
SecurityException- If a security manager, s, is present and the caller's class loader is not the same as or an ancestor of the class loader for the current class and invocation ofs.checkPackageAccess()denies access to the package of this class.- Since:
- 1.1
-
getField
Returns aFieldobject that reflects the specified public member field of the class or interface represented by thisClassobject. Thenameparameter is aStringspecifying the simple name of the desired field.The field to be reflected is determined by the algorithm that follows. Let C be the class or interface represented by this
Classobject:- If C declares a public field with the name specified, that is the field to be reflected.
- If no field was found in step 1 above, this algorithm is applied recursively to each direct superinterface of C. The direct superinterfaces are searched in the order they were declared.
- If no field was found in steps 1 and 2 above, and C has a
superclass S, then this algorithm is invoked recursively upon S.
If C has no superclass, then a
NoSuchFieldExceptionis thrown.
If this
Classobject represents an array type, then this method does not find thelengthfield of the array type.- Parameters:
name- the field name- Returns:
- the
Fieldobject of this class specified byname - Throws:
NoSuchFieldException- if a field with the specified name is not found.NullPointerException- ifnameisnullSecurityException- If a security manager, s, is present and the caller's class loader is not the same as or an ancestor of the class loader for the current class and invocation ofs.checkPackageAccess()denies access to the package of this class.- See Java Language Specification:
-
8.2 Class Members
8.3 Field Declarations - Since:
- 1.1
-
getMethod
public Method getMethod(String name, Class<?>... parameterTypes) throws NoSuchMethodException, SecurityException Returns aMethodobject that reflects the specified public member method of the class or interface represented by thisClassobject. Thenameparameter is aStringspecifying the simple name of the desired method. TheparameterTypesparameter is an array ofClassobjects that identify the method's formal parameter types, in declared order. IfparameterTypesisnull, it is treated as if it were an empty array.If this
Classobject represents an array type, then this method finds any public method inherited by the array type fromObjectexcept methodclone().If this
Classobject represents an interface then this method does not find any implicitly declared method fromObject. Therefore, if no methods are explicitly declared in this interface or any of its superinterfaces, then this method does not find any method.This method does not find any method with name "
<init>" or "<clinit>".Generally, the method to be reflected is determined by the 4 step algorithm that follows. Let C be the class or interface represented by this
Classobject:- A union of methods is composed of:
- C's declared public instance and static methods as returned by
getDeclaredMethods()and filtered to include only public methods that match givennameandparameterTypes - If C is a class other than
Object, then include the result of invoking this algorithm recursively on the superclass of C. - Include the results of invoking this algorithm recursively on all direct superinterfaces of C, but include only instance methods.
- C's declared public instance and static methods as returned by
- This union is partitioned into subsets of methods with same return type (the selection of methods from step 1 also guarantees that they have the same method name and parameter types).
- Within each such subset only the most specific methods are selected.
Let method M be a method from a set of methods with same VM
signature (return type, name, parameter types).
M is most specific if there is no such method N != M from the same
set, such that N is more specific than M. N is more specific than M
if:
- N is declared by a class and M is declared by an interface; or
- N and M are both declared by classes or both by interfaces and N's declaring type is the same as or a subtype of M's declaring type (clearly, if M's and N's declaring types are the same type, then M and N are the same method).
- The result of this algorithm is chosen arbitrarily from the methods
with most specific return type among all selected methods from step 3.
Let R be a return type of a method M from the set of all selected methods
from step 3. M is a method with most specific return type if there is
no such method N != M from the same set, having return type S != R,
such that S is a subtype of R as determined by
R.class.
isAssignableFrom(java.lang.Class<?>)(S.class).
- API Note:
- There may be more than one method with matching name and parameter types in a class because while the Java language forbids a class to declare multiple methods with the same signature but different return types, the Java virtual machine does not. This increased flexibility in the virtual machine can be used to implement various language features. For example, covariant returns can be implemented with bridge methods; the bridge method and the overriding method would have the same signature but different return types. This method would return the overriding method as it would have a more specific return type.
- Parameters:
name- the name of the methodparameterTypes- the list of parameters- Returns:
- the
Methodobject that matches the specifiednameandparameterTypes - Throws:
NoSuchMethodException- if a matching method is not found or if the name is "<init>"or "<clinit>".NullPointerException- ifnameisnullSecurityException- If a security manager, s, is present and the caller's class loader is not the same as or an ancestor of the class loader for the current class and invocation ofs.checkPackageAccess()denies access to the package of this class.- See Java Language Specification:
-
8.2 Class Members
8.4 Method Declarations - Since:
- 1.1
- A union of methods is composed of:
-
getConstructor
public Constructor<T> getConstructor(Class<?>... parameterTypes) throws NoSuchMethodException, SecurityException Returns aConstructorobject that reflects the specified public constructor of the class represented by thisClassobject. TheparameterTypesparameter is an array ofClassobjects that identify the constructor's formal parameter types, in declared order. If thisClassobject represents an inner class declared in a non-static context, the formal parameter types include the explicit enclosing instance as the first parameter.The constructor to reflect is the public constructor of the class represented by this
Classobject whose formal parameter types match those specified byparameterTypes.- Parameters:
parameterTypes- the parameter array- Returns:
- the
Constructorobject of the public constructor that matches the specifiedparameterTypes - Throws:
NoSuchMethodException- if a matching method is not found.SecurityException- If a security manager, s, is present and the caller's class loader is not the same as or an ancestor of the class loader for the current class and invocation ofs.checkPackageAccess()denies access to the package of this class.- Since:
- 1.1
-
getDeclaredClasses
Returns an array ofClassobjects reflecting all the classes and interfaces declared as members of the class represented by thisClassobject. This includes public, protected, default (package) access, and private classes and interfaces declared by the class, but excludes inherited classes and interfaces. This method returns an array of length 0 if the class declares no classes or interfaces as members, or if thisClassobject represents a primitive type, an array class, or void.- Returns:
- the array of
Classobjects representing all the declared members of this class - Throws:
SecurityException- If a security manager, s, is present and any of the following conditions is met:- the caller's class loader is not the same as the
class loader of this class and invocation of
s.checkPermissionmethod withRuntimePermission("accessDeclaredMembers")denies access to the declared classes within this class - the caller's class loader is not the same as or an
ancestor of the class loader for the current class and
invocation of
s.checkPackageAccess()denies access to the package of this class
- the caller's class loader is not the same as the
class loader of this class and invocation of
- See Java Language Specification:
-
8.5 Member Type Declarations
- Since:
- 1.1
-
getDeclaredFields
Returns an array ofFieldobjects reflecting all the fields declared by the class or interface represented by thisClassobject. This includes public, protected, default (package) access, and private fields, but excludes inherited fields.If this
Classobject represents a class or interface with no declared fields, then this method returns an array of length 0.If this
Classobject represents an array type, a primitive type, or void, then this method returns an array of length 0.The elements in the returned array are not sorted and are not in any particular order.
- Returns:
- the array of
Fieldobjects representing all the declared fields of this class - Throws:
SecurityException- If a security manager, s, is present and any of the following conditions is met:- the caller's class loader is not the same as the
class loader of this class and invocation of
s.checkPermissionmethod withRuntimePermission("accessDeclaredMembers")denies access to the declared fields within this class - the caller's class loader is not the same as or an
ancestor of the class loader for the current class and
invocation of
s.checkPackageAccess()denies access to the package of this class
- the caller's class loader is not the same as the
class loader of this class and invocation of
- See Java Language Specification:
-
8.2 Class Members
8.3 Field Declarations - Since:
- 1.1
-
getRecordComponents
Returns an array ofRecordComponentobjects representing all the record components of this record class, ornullif this class is not a record class.The components are returned in the same order that they are declared in the record header. The array is empty if this record class has no components. If the class is not a record class, that is
isRecord()returnsfalse, then this method returnsnull. Conversely, ifisRecord()returnstrue, then this method returns a non-null value.- API Note:
The following method can be used to find the record canonical constructor:
static <T extends Record> Constructor<T> getCanonicalConstructor(Class<T> cls) throws NoSuchMethodException { Class<?>[] paramTypes = Arrays.stream(cls.getRecordComponents()) .map(RecordComponent::getType) .toArray(Class<?>[]::new); return cls.getDeclaredConstructor(paramTypes); }- Returns:
- An array of
RecordComponentobjects representing all the record components of this record class, ornullif this class is not a record class - Throws:
SecurityException- If a security manager, s, is present and any of the following conditions is met:- the caller's class loader is not the same as the
class loader of this class and invocation of
s.checkPermissionmethod withRuntimePermission("accessDeclaredMembers")denies access to the declared methods within this class - the caller's class loader is not the same as or an
ancestor of the class loader for the current class and
invocation of
s.checkPackageAccess()denies access to the package of this class
- the caller's class loader is not the same as the
class loader of this class and invocation of
- See Java Language Specification:
-
8.10 Record Classes
- Since:
- 16
-
getDeclaredMethods
Returns an array containingMethodobjects reflecting all the declared methods of the class or interface represented by thisClassobject, including public, protected, default (package) access, and private methods, but excluding inherited methods. The declared methods may include methods not in the source of the class or interface, including bridge methods and other synthetic methods added by compilers.If this
Classobject represents a class or interface that has multiple declared methods with the same name and parameter types, but different return types, then the returned array has aMethodobject for each such method.If this
Classobject represents a class or interface that has a class initialization method<clinit>, then the returned array does not have a correspondingMethodobject.If this
Classobject represents a class or interface with no declared methods, then the returned array has length 0.If this
Classobject represents an array type, a primitive type, or void, then the returned array has length 0.The elements in the returned array are not sorted and are not in any particular order.
- Returns:
- the array of
Methodobjects representing all the declared methods of this class - Throws:
SecurityException- If a security manager, s, is present and any of the following conditions is met:- the caller's class loader is not the same as the
class loader of this class and invocation of
s.checkPermissionmethod withRuntimePermission("accessDeclaredMembers")denies access to the declared methods within this class - the caller's class loader is not the same as or an
ancestor of the class loader for the current class and
invocation of
s.checkPackageAccess()denies access to the package of this class
- the caller's class loader is not the same as the
class loader of this class and invocation of
- See Java Language Specification:
-
8.2 Class Members
8.4 Method Declarations - Since:
- 1.1
- See Also:
-
getDeclaredConstructors
Returns an array ofConstructorobjects reflecting all the constructors declared by the class represented by thisClassobject. These are public, protected, default (package) access, and private constructors. The elements in the array returned are not sorted and are not in any particular order. If the class has a default constructor, it is included in the returned array. This method returns an array of length 0 if thisClassobject represents an interface, a primitive type, an array class, or void.See The Java Language Specification, section 8.2.
- Returns:
- the array of
Constructorobjects representing all the declared constructors of this class - Throws:
SecurityException- If a security manager, s, is present and any of the following conditions is met:- the caller's class loader is not the same as the
class loader of this class and invocation of
s.checkPermissionmethod withRuntimePermission("accessDeclaredMembers")denies access to the declared constructors within this class - the caller's class loader is not the same as or an
ancestor of the class loader for the current class and
invocation of
s.checkPackageAccess()denies access to the package of this class
- the caller's class loader is not the same as the
class loader of this class and invocation of
- See Java Language Specification:
-
8.8 Constructor Declarations
- Since:
- 1.1
-
getDeclaredField
Returns aFieldobject that reflects the specified declared field of the class or interface represented by thisClassobject. Thenameparameter is aStringthat specifies the simple name of the desired field.If this
Classobject represents an array type, then this method does not find thelengthfield of the array type.- Parameters:
name- the name of the field- Returns:
- the
Fieldobject for the specified field in this class - Throws:
NoSuchFieldException- if a field with the specified name is not found.NullPointerException- ifnameisnullSecurityException- If a security manager, s, is present and any of the following conditions is met:- the caller's class loader is not the same as the
class loader of this class and invocation of
s.checkPermissionmethod withRuntimePermission("accessDeclaredMembers")denies access to the declared field - the caller's class loader is not the same as or an
ancestor of the class loader for the current class and
invocation of
s.checkPackageAccess()denies access to the package of this class
- the caller's class loader is not the same as the
class loader of this class and invocation of
- See Java Language Specification:
-
8.2 Class Members
8.3 Field Declarations - Since:
- 1.1
-
getDeclaredMethod
public Method getDeclaredMethod(String name, Class<?>... parameterTypes) throws NoSuchMethodException, SecurityException Returns aMethodobject that reflects the specified declared method of the class or interface represented by thisClassobject. Thenameparameter is aStringthat specifies the simple name of the desired method, and theparameterTypesparameter is an array ofClassobjects that identify the method's formal parameter types, in declared order. If more than one method with the same parameter types is declared in a class, and one of these methods has a return type that is more specific than any of the others, that method is returned; otherwise one of the methods is chosen arbitrarily. If the name is "<init>"or "<clinit>" aNoSuchMethodExceptionis raised.If this
Classobject represents an array type, then this method does not find theclone()method.- Parameters:
name- the name of the methodparameterTypes- the parameter array- Returns:
- the
Methodobject for the method of this class matching the specified name and parameters - Throws:
NoSuchMethodException- if a matching method is not found.NullPointerException- ifnameisnullSecurityException- If a security manager, s, is present and any of the following conditions is met:- the caller's class loader is not the same as the
class loader of this class and invocation of
s.checkPermissionmethod withRuntimePermission("accessDeclaredMembers")denies access to the declared method - the caller's class loader is not the same as or an
ancestor of the class loader for the current class and
invocation of
s.checkPackageAccess()denies access to the package of this class
- the caller's class loader is not the same as the
class loader of this class and invocation of
- See Java Language Specification:
-
8.2 Class Members
8.4 Method Declarations - Since:
- 1.1
-
getDeclaredConstructor
public Constructor<T> getDeclaredConstructor(Class<?>... parameterTypes) throws NoSuchMethodException, SecurityException Returns aConstructorobject that reflects the specified constructor of the class or interface represented by thisClassobject. TheparameterTypesparameter is an array ofClassobjects that identify the constructor's formal parameter types, in declared order. If thisClassobject represents an inner class declared in a non-static context, the formal parameter types include the explicit enclosing instance as the first parameter.- Parameters:
parameterTypes- the parameter array- Returns:
- The
Constructorobject for the constructor with the specified parameter list - Throws:
NoSuchMethodException- if a matching method is not found.SecurityException- If a security manager, s, is present and any of the following conditions is met:- the caller's class loader is not the same as the
class loader of this class and invocation of
s.checkPermissionmethod withRuntimePermission("accessDeclaredMembers")denies access to the declared constructor - the caller's class loader is not the same as or an
ancestor of the class loader for the current class and
invocation of
s.checkPackageAccess()denies access to the package of this class
- the caller's class loader is not the same as the
class loader of this class and invocation of
- Since:
- 1.1
-
getResourceAsStream
Finds a resource with a given name.If this class is in a named
Modulethen this method will attempt to find the resource in the module. This is done by delegating to the module's class loaderfindResource(String,String)method, invoking it with the module name and the absolute name of the resource. Resources in named modules are subject to the rules for encapsulation specified in theModulegetResourceAsStreammethod and so this method returnsnullwhen the resource is a non-".class" resource in a package that is not open to the caller's module.Otherwise, if this class is not in a named module then the rules for searching resources associated with a given class are implemented by the defining class loader of the class. This method delegates to this
Classobject's class loader. If thisClassobject was loaded by the bootstrap class loader, the method delegates toClassLoader.getSystemResourceAsStream(java.lang.String).Before delegation, an absolute resource name is constructed from the given resource name using this algorithm:
- If the
namebegins with a'/'('\u002f'), then the absolute name of the resource is the portion of thenamefollowing the'/'. - Otherwise, the absolute name is of the following form:
modified_package_name/nameWhere the
modified_package_nameis the package name of this object with'/'substituted for'.'('\u002e').
- Parameters:
name- name of the desired resource- Returns:
- A
InputStreamobject;nullif no resource with this name is found, the resource is in a package that is not open to at least the caller module, or access to the resource is denied by the security manager. - Throws:
NullPointerException- Ifnameisnull- Since:
- 1.1
- See Also:
- If the
-
getResource
Finds a resource with a given name.If this class is in a named
Modulethen this method will attempt to find the resource in the module. This is done by delegating to the module's class loaderfindResource(String,String)method, invoking it with the module name and the absolute name of the resource. Resources in named modules are subject to the rules for encapsulation specified in theModulegetResourceAsStreammethod and so this method returnsnullwhen the resource is a non-".class" resource in a package that is not open to the caller's module.Otherwise, if this class is not in a named module then the rules for searching resources associated with a given class are implemented by the defining class loader of the class. This method delegates to this
Classobject's class loader. If thisClassobject was loaded by the bootstrap class loader, the method delegates toClassLoader.getSystemResource(java.lang.String).Before delegation, an absolute resource name is constructed from the given resource name using this algorithm:
- If the
namebegins with a'/'('\u002f'), then the absolute name of the resource is the portion of thenamefollowing the'/'. - Otherwise, the absolute name is of the following form:
modified_package_name/nameWhere the
modified_package_nameis the package name of this object with'/'substituted for'.'('\u002e').
- Parameters:
name- name of the desired resource- Returns:
- A
URLobject;nullif no resource with this name is found, the resource cannot be located by a URL, the resource is in a package that is not open to at least the caller module, or access to the resource is denied by the security manager. - Throws:
NullPointerException- Ifnameisnull- Since:
- 1.1
- If the
-
getProtectionDomain
Returns theProtectionDomainof this class. If there is a security manager installed, this method first calls the security manager'scheckPermissionmethod with aRuntimePermission("getProtectionDomain")permission to ensure it's ok to get theProtectionDomain.- Returns:
- the ProtectionDomain of this class
- Throws:
SecurityException- if a security manager exists and itscheckPermissionmethod doesn't allow getting the ProtectionDomain.- Since:
- 1.2
- See Also:
-
desiredAssertionStatus
public boolean desiredAssertionStatus()Returns the assertion status that would be assigned to this class if it were to be initialized at the time this method is invoked. If this class has had its assertion status set, the most recent setting will be returned; otherwise, if any package default assertion status pertains to this class, the most recent setting for the most specific pertinent package default assertion status is returned; otherwise, if this class is not a system class (i.e., it has a class loader) its class loader's default assertion status is returned; otherwise, the system class default assertion status is returned.- API Note:
- Few programmers will have any need for this method; it is provided for the benefit of the JDK itself. (It allows a class to determine at the time that it is initialized whether assertions should be enabled.) Note that this method is not guaranteed to return the actual assertion status that was (or will be) associated with the specified class when it was (or will be) initialized.
- Returns:
- the desired assertion status of the specified class.
- Since:
- 1.4
- See Also:
-
isEnum
public boolean isEnum()Returns true if and only if this class was declared as an enum in the source code. Note thatEnumis not itself an enum class. Also note that if an enum constant is declared with a class body, the class of that enum constant object is an anonymous class and not the class of the declaring enum class. TheEnum.getDeclaringClass()method of an enum constant can be used to get the class of the enum class declaring the constant.- Returns:
- true if and only if this class was declared as an enum in the source code
- See Java Language Specification:
-
8.9.1 Enum Constants
- Since:
- 1.5
-
isRecord
public boolean isRecord()Returnstrueif and only if this class is a record class.The direct superclass of a record class is
java.lang.Record. A record class is final. A record class has (possibly zero) record components;getRecordComponents()returns a non-null but possibly empty value for a record.Note that class
Recordis not a record class and thus invoking this method on classRecordreturnsfalse.- Returns:
- true if and only if this class is a record class, otherwise false
- See Java Language Specification:
-
8.10 Record Classes
- Since:
- 16
-
getEnumConstants
Returns the elements of this enum class or null if this Class object does not represent an enum class.- Returns:
- an array containing the values comprising the enum class
represented by this
Classobject in the order they're declared, or null if thisClassobject does not represent an enum class - See Java Language Specification:
-
8.9.1 Enum Constants
- Since:
- 1.5
-
cast
Casts an object to the class or interface represented by thisClassobject.- Parameters:
obj- the object to be cast- Returns:
- the object after casting, or null if obj is null
- Throws:
ClassCastException- if the object is not null and is not assignable to the type T.- Since:
- 1.5
-
asSubclass
Casts thisClassobject to represent a subclass of the class represented by the specified class object. Checks that the cast is valid, and throws aClassCastExceptionif it is not. If this method succeeds, it always returns a reference to thisClassobject.This method is useful when a client needs to "narrow" the type of a
Classobject to pass it to an API that restricts theClassobjects that it is willing to accept. A cast would generate a compile-time warning, as the correctness of the cast could not be checked at runtime (because generic types are implemented by erasure).- Type Parameters:
U- the type to cast thisClassobject to- Parameters:
clazz- the class of the type to cast thisClassobject to- Returns:
- this
Classobject, cast to represent a subclass of the specified class object. - Throws:
ClassCastException- if thisClassobject does not represent a subclass of the specified class (here "subclass" includes the class itself).- Since:
- 1.5
-
getAnnotation
Returns this element's annotation for the specified type if such an annotation is present, else null.Note that any annotation returned by this method is a declaration annotation.
- Specified by:
getAnnotationin interfaceAnnotatedElement- Type Parameters:
A- the type of the annotation to query for and return if present- Parameters:
annotationClass- the Class object corresponding to the annotation type- Returns:
- this element's annotation for the specified annotation type if present on this element, else null
- Throws:
NullPointerException- if the given annotation class is null- Since:
- 1.5
-
isAnnotationPresent
Returns true if an annotation for the specified type is present on this element, else false. This method is designed primarily for convenient access to marker annotations.The truth value returned by this method is equivalent to:
getAnnotation(annotationClass) != null- Specified by:
isAnnotationPresentin interfaceAnnotatedElement- Parameters:
annotationClass- the Class object corresponding to the annotation type- Returns:
- true if an annotation for the specified annotation type is present on this element, else false
- Throws:
NullPointerException- if the given annotation class is null- Since:
- 1.5
-
getAnnotationsByType
Returns annotations that are associated with this element. If there are no annotations associated with this element, the return value is an array of length 0. The difference between this method andAnnotatedElement.getAnnotation(Class)is that this method detects if its argument is a repeatable annotation type (JLS 9.6), and if so, attempts to find one or more annotations of that type by "looking through" a container annotation. The caller of this method is free to modify the returned array; it will have no effect on the arrays returned to other callers.Note that any annotations returned by this method are declaration annotations.
- Specified by:
getAnnotationsByTypein interfaceAnnotatedElement- Type Parameters:
A- the type of the annotation to query for and return if present- Parameters:
annotationClass- the Class object corresponding to the annotation type- Returns:
- all this element's annotations for the specified annotation type if associated with this element, else an array of length zero
- Throws:
NullPointerException- if the given annotation class is null- Since:
- 1.8
-
getAnnotations
Returns annotations that are present on this element. If there are no annotations present on this element, the return value is an array of length 0. The caller of this method is free to modify the returned array; it will have no effect on the arrays returned to other callers.Note that any annotations returned by this method are declaration annotations.
- Specified by:
getAnnotationsin interfaceAnnotatedElement- Returns:
- annotations present on this element
- Since:
- 1.5
-
getDeclaredAnnotation
Returns this element's annotation for the specified type if such an annotation is directly present, else null. This method ignores inherited annotations. (Returns null if no annotations are directly present on this element.)Note that any annotation returned by this method is a declaration annotation.
- Specified by:
getDeclaredAnnotationin interfaceAnnotatedElement- Type Parameters:
A- the type of the annotation to query for and return if directly present- Parameters:
annotationClass- the Class object corresponding to the annotation type- Returns:
- this element's annotation for the specified annotation type if directly present on this element, else null
- Throws:
NullPointerException- if the given annotation class is null- Since:
- 1.8
-
getDeclaredAnnotationsByType
Returns this element's annotation(s) for the specified type if such annotations are either directly present or indirectly present. This method ignores inherited annotations. If there are no specified annotations directly or indirectly present on this element, the return value is an array of length 0. The difference between this method andAnnotatedElement.getDeclaredAnnotation(Class)is that this method detects if its argument is a repeatable annotation type (JLS 9.6), and if so, attempts to find one or more annotations of that type by "looking through" a container annotation if one is present. The caller of this method is free to modify the returned array; it will have no effect on the arrays returned to other callers.Note that any annotations returned by this method are declaration annotations.
- Specified by:
getDeclaredAnnotationsByTypein interfaceAnnotatedElement- Type Parameters:
A- the type of the annotation to query for and return if directly or indirectly present- Parameters:
annotationClass- the Class object corresponding to the annotation type- Returns:
- all this element's annotations for the specified annotation type if directly or indirectly present on this element, else an array of length zero
- Throws:
NullPointerException- if the given annotation class is null- Since:
- 1.8
-
getDeclaredAnnotations
Returns annotations that are directly present on this element. This method ignores inherited annotations. If there are no annotations directly present on this element, the return value is an array of length 0. The caller of this method is free to modify the returned array; it will have no effect on the arrays returned to other callers.Note that any annotations returned by this method are declaration annotations.
- Specified by:
getDeclaredAnnotationsin interfaceAnnotatedElement- Returns:
- annotations directly present on this element
- Since:
- 1.5
-
getAnnotatedSuperclass
Returns anAnnotatedTypeobject that represents the use of a type to specify the superclass of the entity represented by thisClassobject. (The use of type Foo to specify the superclass in '... extends Foo' is distinct from the declaration of class Foo.)If this
Classobject represents a class whose declaration does not explicitly indicate an annotated superclass, then the return value is anAnnotatedTypeobject representing an element with no annotations.If this
Classrepresents either theObjectclass, an interface type, an array type, a primitive type, or void, the return value isnull.- Returns:
- an object representing the superclass
- Since:
- 1.8
-
getAnnotatedInterfaces
Returns an array ofAnnotatedTypeobjects that represent the use of types to specify superinterfaces of the entity represented by thisClassobject. (The use of type Foo to specify a superinterface in '... implements Foo' is distinct from the declaration of interface Foo.)If this
Classobject represents a class, the return value is an array containing objects representing the uses of interface types to specify interfaces implemented by the class. The order of the objects in the array corresponds to the order of the interface types used in the 'implements' clause of the declaration of thisClassobject.If this
Classobject represents an interface, the return value is an array containing objects representing the uses of interface types to specify interfaces directly extended by the interface. The order of the objects in the array corresponds to the order of the interface types used in the 'extends' clause of the declaration of thisClassobject.If this
Classobject represents a class or interface whose declaration does not explicitly indicate any annotated superinterfaces, the return value is an array of length 0.If this
Classobject represents either theObjectclass, an array type, a primitive type, or void, the return value is an array of length 0.- Returns:
- an array representing the superinterfaces
- Since:
- 1.8
-
getNestHost
Returns the nest host of the nest to which the class or interface represented by thisClassobject belongs. Every class and interface belongs to exactly one nest. If the nest host of this class or interface has previously been determined, then this method returns the nest host. If the nest host of this class or interface has not previously been determined, then this method determines the nest host using the algorithm of JVMS 5.4.4, and returns it. Often, a class or interface belongs to a nest consisting only of itself, in which case this method returnsthisto indicate that the class or interface is the nest host.If this
Classobject represents a primitive type, an array type, orvoid, then this method returnsthis, indicating that the represented entity belongs to the nest consisting only of itself, and is the nest host.- Returns:
- the nest host of this class or interface
- Throws:
SecurityException- If the returned class is not the current class, and if a security manager, s, is present and the caller's class loader is not the same as or an ancestor of the class loader for the returned class and invocation ofs.checkPackageAccess()denies access to the package of the returned class- See Java Virtual Machine Specification:
-
4.7.28 The
NestHostAttribute
4.7.29 TheNestMembersAttribute
5.4.4 Access Control - Since:
- 11
-
isNestmateOf
Determines if the givenClassis a nestmate of the class or interface represented by thisClassobject. Two classes or interfaces are nestmates if they have the same nest host.- Parameters:
c- the class to check- Returns:
trueif this class andcare members of the same nest; andfalseotherwise.- Since:
- 11
-
getNestMembers
Returns an array containingClassobjects representing all the classes and interfaces that are members of the nest to which the class or interface represented by thisClassobject belongs. First, this method obtains the nest host,H, of the nest to which the class or interface represented by thisClassobject belongs. The zeroth element of the returned array isH. Then, for each class or interfaceCwhich is recorded byHas being a member of its nest, this method attempts to obtain theClassobject forC(using the defining class loader of the currentClassobject), and then obtains the nest host of the nest to whichCbelongs. The classes and interfaces which are recorded byHas being members of its nest, and for whichHcan be determined as their nest host, are indicated by subsequent elements of the returned array. The order of such elements is unspecified. Duplicates are permitted.If this
Classobject represents a primitive type, an array type, orvoid, then this method returns a single-element array containingthis.- API Note:
- The returned array includes only the nest members recorded in the
NestMembersattribute, and not any hidden classes that were added to the nest viaLookup::defineHiddenClass. - Returns:
- an array of all classes and interfaces in the same nest as this class or interface
- Throws:
SecurityException- If any returned class is not the current class, and if a security manager, s, is present and the caller's class loader is not the same as or an ancestor of the class loader for that returned class and invocation ofs.checkPackageAccess()denies access to the package of that returned class- See Java Virtual Machine Specification:
-
4.7.28 The
NestHostAttribute
4.7.29 TheNestMembersAttribute - Since:
- 11
- See Also:
-
descriptorString
Returns the descriptor string of the entity (class, interface, array class, primitive type, orvoid) represented by thisClassobject.If this
Classobject represents a class or interface, not an array class, then:- If the class or interface is not hidden,
then the result is a field descriptor (JVMS 4.3.2)
for the class or interface. Calling
ClassDesc::ofDescriptorwith the result descriptor string produces aClassDescdescribing this class or interface. - If the class or interface is hidden,
then the result is a string of the form:
where N is the binary name encoded in internal form indicated by the"L" +N+ "." + <suffix> + ";"classfile passed toLookup::defineHiddenClass, and<suffix>is an unqualified name. A hidden class or interface has no nominal descriptor. The result string is not a type descriptor.
If this
Classobject represents an array class, then the result is a string consisting of one or more '[' characters representing the depth of the array nesting, followed by the descriptor string of the element type.- If the element type is not a hidden class
or interface, then this array class can be described nominally.
Calling
ClassDesc::ofDescriptorwith the result descriptor string produces aClassDescdescribing this array class. - If the element type is a hidden class or interface, then this array class cannot be described nominally. The result string is not a type descriptor.
If this
Classobject represents a primitive type orvoid, then the result is a field descriptor string which is a one-letter code corresponding to a primitive type orvoid("B", "C", "D", "F", "I", "J", "S", "Z", "V") (JVMS 4.3.2).- Specified by:
descriptorStringin interfaceTypeDescriptor- API Note:
- This is not a strict inverse of
forName(java.lang.String); distinct classes which share a common name but have different class loaders will have identical descriptor strings. - Returns:
- the descriptor string for this
Classobject - See Java Virtual Machine Specification:
-
4.3.2 Field Descriptors
- Since:
- 12
- If the class or interface is not hidden,
then the result is a field descriptor (JVMS 4.3.2)
for the class or interface. Calling
-
componentType
Returns the component type of thisClass, if it describes an array type, ornullotherwise.- Specified by:
componentTypein interfaceTypeDescriptor.OfField<T>- Implementation Requirements:
- Equivalent to
getComponentType(). - Returns:
- a
Classdescribing the component type, ornullif thisClassdoes not describe an array type - Since:
- 12
-
arrayType
Returns aClassfor an array type whose component type is described by this Class.- Specified by:
arrayTypein interfaceTypeDescriptor.OfField<T>- Returns:
- a
Classdescribing the array type - Since:
- 12
-
describeConstable
Returns a nominal descriptor for this instance, if one can be constructed, or an emptyOptionalif one cannot be.- Specified by:
describeConstablein interfaceConstable- Returns:
- An
Optionalcontaining the resulting nominal descriptor, or an emptyOptionalif one cannot be constructed. - Since:
- 12
-
isHidden
public boolean isHidden()Returnstrueif and only if the underlying class is a hidden class.- Returns:
trueif and only if this class is a hidden class.- Since:
- 15
- See Also:
-
getPermittedSubclasses
Returns an array containingClassobjects representing the direct subinterfaces or subclasses permitted to extend or implement this class or interface if it is sealed. The order of such elements is unspecified. The array is empty if this sealed class or interface has no permitted subclass. If thisClassobject represents a primitive type,void, an array type, or a class or interface that is not sealed, that isisSealed()returnsfalse, then this method returnsnull. Conversely, ifisSealed()returnstrue, then this method returns a non-null value. For each class or interfaceCwhich is recorded as a permitted direct subinterface or subclass of this class or interface, this method attempts to obtain theClassobject forC(using the defining class loader of the currentClassobject). TheClassobjects which can be obtained and which are direct subinterfaces or subclasses of this class or interface, are indicated by elements of the returned array. If aClassobject cannot be obtained, it is silently ignored, and not included in the result array.- Returns:
- an array of
Classobjects of the permitted subclasses of this class or interface, ornullif this class or interface is not sealed. - Throws:
SecurityException- If a security manager, s, is present and the caller's class loader is not the same as or an ancestor of the class loader for that returned class and invocation ofs.checkPackageAccess()denies access to the package of any class in the returned array.- See Java Language Specification:
-
8.1 Class Declarations
9.1 Interface Declarations - Since:
- 17
-
isSealed
public boolean isSealed()Returnstrueif and only if thisClassobject represents a sealed class or interface. If thisClassobject represents a primitive type,void, or an array type, this method returnsfalse. A sealed class or interface has (possibly zero) permitted subclasses;getPermittedSubclasses()returns a non-null but possibly empty value for a sealed class or interface.- Returns:
trueif and only if thisClassobject represents a sealed class or interface.- See Java Language Specification:
-
8.1 Class Declarations
9.1 Interface Declarations - Since:
- 17
-