- java.lang.Object
-
- java.lang.Class<T>
-
- Type Parameters:
T
- the type of the class modeled by thisClass
object. For example, the type ofString.class
isClass<String>
. UseClass<?>
if the class being modeled is unknown.
- All Implemented Interfaces:
- Serializable, AnnotatedElement, GenericDeclaration, Type
public final class Class<T> extends Object implements Serializable, GenericDeclaration, Type, AnnotatedElement
Instances of the classClass
represent classes and interfaces in a running Java application. An enum is a kind of class and an annotation is a kind of interface. Every array also belongs to a class that is reflected as aClass
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
, anddouble
), and the keywordvoid
are also represented asClass
objects.Class
has no public constructor. InsteadClass
objects are constructed automatically by the Java Virtual Machine as classes are loaded and by calls to thedefineClass
method in the class loader.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 type (or for void) using a class literal. See Section 15.8.2 of The Java™ Language Specification. For example:System.out.println("The name of class Foo is: "+Foo.class.getName());
- Since:
- JDK1.0
- See Also:
ClassLoader.defineClass(byte[], int, int)
, Serialized Form
-
-
Method Summary
Methods Modifier and Type Method and Description <U> Class<? extends U>
asSubclass(Class<U> clazz)
Casts thisClass
object to represent a subclass of the class represented by the specified class object.T
cast(Object obj)
Casts an object to the class or interface represented by thisClass
object.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.static Class<?>
forName(String className)
Returns theClass
object associated with the class or interface with the given string name.static Class<?>
forName(String name, boolean initialize, ClassLoader loader)
Returns theClass
object associated with the class or interface with the given string name, using the given class loader.<A extends Annotation>
AgetAnnotation(Class<A> annotationClass)
Returns this element's annotation for the specified type if such an annotation is present, else null.Annotation[]
getAnnotations()
Returns all annotations present on this element.String
getCanonicalName()
Returns the canonical name of the underlying class as defined by the Java Language Specification.Class<?>[]
getClasses()
Returns an array containingClass
objects representing all the public classes and interfaces that are members of the class represented by thisClass
object.ClassLoader
getClassLoader()
Returns the class loader for the class.Class<?>
getComponentType()
Returns theClass
representing the component type of an array.Constructor<T>
getConstructor(Class<?>... parameterTypes)
Returns aConstructor
object that reflects the specified public constructor of the class represented by thisClass
object.Constructor<?>[]
getConstructors()
Returns an array containingConstructor
objects reflecting all the public constructors of the class represented by thisClass
object.Annotation[]
getDeclaredAnnotations()
Returns all annotations that are directly present on this element.Class<?>[]
getDeclaredClasses()
Returns an array ofClass
objects reflecting all the classes and interfaces declared as members of the class represented by thisClass
object.Constructor<T>
getDeclaredConstructor(Class<?>... parameterTypes)
Returns aConstructor
object that reflects the specified constructor of the class or interface represented by thisClass
object.Constructor<?>[]
getDeclaredConstructors()
Returns an array ofConstructor
objects reflecting all the constructors declared by the class represented by thisClass
object.Field
getDeclaredField(String name)
Returns aField
object that reflects the specified declared field of the class or interface represented by thisClass
object.Field[]
getDeclaredFields()
Returns an array ofField
objects reflecting all the fields declared by the class or interface represented by thisClass
object.Method
getDeclaredMethod(String name, Class<?>... parameterTypes)
Returns aMethod
object that reflects the specified declared method of the class or interface represented by thisClass
object.Method[]
getDeclaredMethods()
Returns an array ofMethod
objects reflecting all the methods declared by the class or interface represented by thisClass
object.Class<?>
getDeclaringClass()
If the class or interface represented by thisClass
object is a member of another class, returns theClass
object representing the class in which it was declared.Class<?>
getEnclosingClass()
Returns the immediately enclosing class of the underlying class.Constructor<?>
getEnclosingConstructor()
If thisClass
object represents a local or anonymous class within a constructor, returns aConstructor
object representing the immediately enclosing constructor of the underlying class.Method
getEnclosingMethod()
If thisClass
object represents a local or anonymous class within a method, returns aMethod
object representing the immediately enclosing method of the underlying class.T[]
getEnumConstants()
Returns the elements of this enum class or null if this Class object does not represent an enum type.Field
getField(String name)
Returns aField
object that reflects the specified public member field of the class or interface represented by thisClass
object.Field[]
getFields()
Returns an array containingField
objects reflecting all the accessible public fields of the class or interface represented by thisClass
object.Type[]
getGenericInterfaces()
Returns theType
s representing the interfaces directly implemented by the class or interface represented by this object.Type
getGenericSuperclass()
Returns theType
representing the direct superclass of the entity (class, interface, primitive type or void) represented by thisClass
.Class<?>[]
getInterfaces()
Determines the interfaces implemented by the class or interface represented by this object.Method
getMethod(String name, Class<?>... parameterTypes)
Returns aMethod
object that reflects the specified public member method of the class or interface represented by thisClass
object.Method[]
getMethods()
Returns an array containingMethod
objects reflecting all the public member methods of the class or interface represented by thisClass
object, including those declared by the class or interface and those inherited from superclasses and superinterfaces.int
getModifiers()
Returns the Java language modifiers for this class or interface, encoded in an integer.String
getName()
Returns the name of the entity (class, interface, array class, primitive type, or void) represented by thisClass
object, as aString
.Package
getPackage()
Gets the package for this class.ProtectionDomain
getProtectionDomain()
Returns theProtectionDomain
of this class.URL
getResource(String name)
Finds a resource with a given name.InputStream
getResourceAsStream(String name)
Finds a resource with a given name.Object[]
getSigners()
Gets the signers of this class.String
getSimpleName()
Returns the simple name of the underlying class as given in the source code.Class<? super T>
getSuperclass()
Returns theClass
representing the superclass of the entity (class, interface, primitive type or void) represented by thisClass
.TypeVariable<Class<T>>[]
getTypeParameters()
Returns an array ofTypeVariable
objects that represent the type variables declared by the generic declaration represented by thisGenericDeclaration
object, in declaration order.boolean
isAnnotation()
Returns true if thisClass
object represents an annotation type.boolean
isAnnotationPresent(Class<? extends Annotation> annotationClass)
Returns true if an annotation for the specified type is present on this element, else false.boolean
isAnonymousClass()
Returnstrue
if and only if the underlying class is an anonymous class.boolean
isArray()
Determines if thisClass
object represents an array class.boolean
isAssignableFrom(Class<?> cls)
Determines if the class or interface represented by thisClass
object is either the same as, or is a superclass or superinterface of, the class or interface represented by the specifiedClass
parameter.boolean
isEnum()
Returns true if and only if this class was declared as an enum in the source code.boolean
isInstance(Object obj)
Determines if the specifiedObject
is assignment-compatible with the object represented by thisClass
.boolean
isInterface()
Determines if the specifiedClass
object represents an interface type.boolean
isLocalClass()
Returnstrue
if and only if the underlying class is a local class.boolean
isMemberClass()
Returnstrue
if and only if the underlying class is a member class.boolean
isPrimitive()
Determines if the specifiedClass
object represents a primitive type.boolean
isSynthetic()
Returnstrue
if this class is a synthetic class; returnsfalse
otherwise.T
newInstance()
Creates a new instance of the class represented by thisClass
object.String
toString()
Converts the object to a string.
-
-
-
Method Detail
-
toString
public String toString()
Converts the object to a string. The string representation is the string "class" or "interface", followed by a space, and then by the fully qualified name of the class in the format returned bygetName
. If thisClass
object represents a primitive type, this method returns the name of the primitive type. If thisClass
object represents void this method returns "void".
-
forName
public static Class<?> forName(String className) throws ClassNotFoundException
Returns theClass
object associated with the class or interface with the given string name. Invoking this method is equivalent to:Class.forName(className, true, currentLoader)
currentLoader
denotes the defining class loader of the current class.For example, the following code fragment returns the runtime
Class
descriptor for the class namedjava.lang.Thread
:Class t = Class.forName("java.lang.Thread")
A call to
forName("X")
causes the class namedX
to be initialized.- Parameters:
className
- the fully qualified name of the desired class.- Returns:
- the
Class
object 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
-
forName
public static Class<?> forName(String name, boolean initialize, ClassLoader loader) throws ClassNotFoundException
Returns theClass
object 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, load, and link the class or interface. The specified class loader is used to load the class or interface. If the parameterloader
is null, the class is loaded through the bootstrap class loader. The class is initialized only if theinitialize
parameter istrue
and if it has not been initialized earlier.If
name
denotes 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 theClass
objects representing primitive types or void.If
name
denotes an array class, the component type of the array class is loaded but not initialized.For example, in an instance method the expression:
Class.forName("Foo")
Class.forName("Foo", true, this.getClass().getClassLoader())
If the
loader
isnull
, and a security manager is present, and the caller's class loader is not null, then this method calls the security manager'scheckPermission
method with aRuntimePermission("getClassLoader")
permission to ensure it's ok to access the bootstrap class loader.- Parameters:
name
- fully qualified name of the desired classinitialize
- whether the class must be initializedloader
- 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 loader- Since:
- 1.2
- See Also:
forName(String)
,ClassLoader
-
newInstance
public T newInstance() throws InstantiationException, IllegalAccessException
Creates a new instance of the class represented by thisClass
object. The class is instantiated as if by anew
expression with an empty argument list. The class is initialized if it has not already been initialized.Note that 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. The
Constructor.newInstance
method avoids this problem by wrapping any exception thrown by the constructor in a (checked)InvocationTargetException
.- 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 thisClass
represents 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 any of the following conditions is met:- invocation of
s.checkMemberAccess(this, Member.PUBLIC)
denies creation of new instances of 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
- invocation of
-
isInstance
public boolean isInstance(Object obj)
Determines if the specifiedObject
is assignment-compatible with the object represented by thisClass
. This method is the dynamic equivalent of the Java languageinstanceof
operator. The method returnstrue
if the specifiedObject
argument is non-null and can be cast to the reference type represented by thisClass
object without raising aClassCastException.
It returnsfalse
otherwise.Specifically, if this
Class
object represents a declared class, this method returnstrue
if the specifiedObject
argument is an instance of the represented class (or of any of its subclasses); it returnsfalse
otherwise. If thisClass
object represents an array class, this method returnstrue
if the specifiedObject
argument can be converted to an object of the array class by an identity conversion or by a widening reference conversion; it returnsfalse
otherwise. If thisClass
object represents an interface, this method returnstrue
if the class or any superclass of the specifiedObject
argument implements this interface; it returnsfalse
otherwise. If thisClass
object represents a primitive type, this method returnsfalse
.- Parameters:
obj
- the object to check- Returns:
- true if
obj
is an instance of this class - Since:
- JDK1.1
-
isAssignableFrom
public boolean isAssignableFrom(Class<?> cls)
Determines if the class or interface represented by thisClass
object is either the same as, or is a superclass or superinterface of, the class or interface represented by the specifiedClass
parameter. It returnstrue
if so; otherwise it returnsfalse
. If thisClass
object represents a primitive type, this method returnstrue
if the specifiedClass
parameter is exactly thisClass
object; otherwise it returnsfalse
.Specifically, this method tests whether the type represented by the specified
Class
parameter can be converted to the type represented by thisClass
object 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
- theClass
object to be checked- Returns:
- the
boolean
value indicating whether objects of the typecls
can be assigned to objects of this class - Throws:
NullPointerException
- if the specified Class parameter is null.- Since:
- JDK1.1
-
isInterface
public boolean isInterface()
Determines if the specifiedClass
object represents an interface type.- Returns:
true
if this object represents an interface;false
otherwise.
-
isArray
public boolean isArray()
Determines if thisClass
object represents an array class.- Returns:
true
if this object represents an array class;false
otherwise.- Since:
- JDK1.1
-
isPrimitive
public boolean isPrimitive()
Determines if the specifiedClass
object represents a primitive type.There are nine predefined
Class
objects 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
Class
objects for which this method returnstrue
.- Returns:
- true if and only if this class represents a primitive type
- Since:
- JDK1.1
- See Also:
Boolean.TYPE
,Character.TYPE
,Byte.TYPE
,Short.TYPE
,Integer.TYPE
,Long.TYPE
,Float.TYPE
,Double.TYPE
,Void.TYPE
-
isAnnotation
public boolean isAnnotation()
Returns true if thisClass
object represents an annotation type. Note that if this method returns true,isInterface()
would also return true, as all annotation types are also interfaces.- Returns:
true
if this class object represents an annotation type;false
otherwise- Since:
- 1.5
-
isSynthetic
public boolean isSynthetic()
Returnstrue
if this class is a synthetic class; returnsfalse
otherwise.- Returns:
true
if and only if this class is a synthetic class as defined by the Java Language Specification.- Since:
- 1.5
-
getName
public String getName()
Returns the name of the entity (class, interface, array class, primitive type, or void) represented by thisClass
object, as aString
.If this class object represents a reference type that is not an array type then the binary name of the class is returned, as specified by The Java™ Language Specification.
If this class object represents a primitive type or void, then the name returned is a
String
equal to the Java language keyword corresponding to the primitive type or void.If this class object represents a class of arrays, then the internal form of the name consists of the name of the element type preceded by one or more '
[
' characters representing the depth of the array nesting. The encoding of element type names is as follows:Element Type Encoding boolean Z byte B char C class or interface Lclassname; double D float F int I long J short S The class or interface name classname is the binary name of the class specified above.
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 or interface represented by this object.
-
getClassLoader
public ClassLoader 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 a security manager is present, and the caller's class loader is not null and the caller's class loader is not the same as or an ancestor of the class loader for the class whose class loader is requested, then this method calls the security manager's
checkPermission
method with aRuntimePermission("getClassLoader")
permission to ensure it's ok to access the class loader for the class.If this object represents a primitive type or void, null is returned.
- Returns:
- the class loader that loaded the class or interface represented by this object.
- Throws:
SecurityException
- if a security manager exists and itscheckPermission
method denies access to the class loader for the class.- See Also:
ClassLoader
,SecurityManager.checkPermission(java.security.Permission)
,RuntimePermission
-
getTypeParameters
public TypeVariable<Class<T>>[] getTypeParameters()
Returns an array ofTypeVariable
objects that represent the type variables declared by the generic declaration represented by thisGenericDeclaration
object, in declaration order. Returns an array of length 0 if the underlying generic declaration declares no type variables.- Specified by:
getTypeParameters
in interfaceGenericDeclaration
- Returns:
- an array of
TypeVariable
objects 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 The Java™ Virtual Machine Specification- Since:
- 1.5
-
getSuperclass
public Class<? super T> getSuperclass()
Returns theClass
representing the superclass of the entity (class, interface, primitive type or void) represented by thisClass
. If thisClass
represents either theObject
class, an interface, a primitive type, or void, then null is returned. If this object represents an array class then theClass
object representing theObject
class is returned.- Returns:
- the superclass of the class represented by this object.
-
getGenericSuperclass
public Type getGenericSuperclass()
Returns theType
representing the direct superclass of the entity (class, interface, primitive type or void) represented by thisClass
.If the superclass is a parameterized type, the
Type
object returned must accurately reflect the actual type parameters used in the source code. The parameterized type representing the superclass is created if it had not been created before. See the declaration ofParameterizedType
for the semantics of the creation process for parameterized types. If thisClass
represents either theObject
class, an interface, a primitive type, or void, then null is returned. If this object represents an array class then theClass
object representing theObject
class is returned.- Returns:
- the superclass of the class represented by this object
- Throws:
GenericSignatureFormatError
- if the generic class signature does not conform to the format specified in 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
public Package getPackage()
Gets the package for this class. The class loader of this class is used to find the package. If the class was loaded by the bootstrap class loader the set of packages loaded from CLASSPATH is searched to find the package of the class. Null is returned if no package object was created by the class loader of this class.Packages have attributes for versions and specifications only if the information was defined in the manifests that accompany the classes, and if the class loader created the package instance with the attributes from the manifest.
- Returns:
- the package of the class, or null if no package information is available from the archive or codebase.
-
getInterfaces
public Class<?>[] getInterfaces()
Determines the interfaces implemented by the class or interface represented by this object.If this object represents a class, the return value is an array containing objects representing all interfaces implemented by the class. The order of the interface objects in the array corresponds to the order of the interface names in the
implements
clause of the declaration of the class represented by this object. For example, given the declaration:class Shimmer implements FloorWax, DessertTopping { ... }
s
is an instance ofShimmer
; the value of the expression:s.getClass().getInterfaces()[0]
Class
object that represents interfaceFloorWax
; and the value of:s.getClass().getInterfaces()[1]
Class
object that represents interfaceDessertTopping
.If this object represents an interface, the array contains objects representing all interfaces extended by the interface. The order of the interface objects in the array corresponds to the order of the interface names in the
extends
clause of the declaration of the interface represented by this object.If this object represents a class or interface that implements no interfaces, the method returns an array of length 0.
If this object represents a primitive type or void, the method returns an array of length 0.
- Returns:
- an array of interfaces implemented by this class.
-
getGenericInterfaces
public Type[] getGenericInterfaces()
Returns theType
s representing the interfaces directly implemented by the class or interface represented by this object.If a superinterface is a parameterized type, the
Type
object returned for it must accurately reflect the actual type parameters used in the source code. The parameterized type representing each superinterface is created if it had not been created before. See the declaration ofParameterizedType
for the semantics of the creation process for parameterized types.If this object represents a class, the return value is an array containing objects representing all interfaces implemented by the class. The order of the interface objects in the array corresponds to the order of the interface names in the
implements
clause of the declaration of the class represented by this object. In the case of an array class, the interfacesCloneable
andSerializable
are returned in that order.If this object 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 the
extends
clause of the declaration of the interface represented by this object.If this object represents a class or interface that implements no interfaces, the method returns an array of length 0.
If this object represents a primitive type or void, the method returns an array of length 0.
- Returns:
- an array of interfaces implemented by this class
- Throws:
GenericSignatureFormatError
- if the generic class signature does not conform to the format specified in 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
public Class<?> getComponentType()
Returns theClass
representing the component type of an array. If this class does not represent an array class this method returns null.- Returns:
- the
Class
representing the component type of this class if this class is an array - Since:
- JDK1.1
- See Also:
Array
-
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
,abstract
andinterface
; they should be decoded using the methods of classModifier
.If the underlying class is an array class, then its
public
,private
andprotected
modifiers are the same as those of its component type. If thisClass
represents a primitive type or void, itspublic
modifier is alwaystrue
, and itsprotected
andprivate
modifiers are alwaysfalse
. If this object represents an array class, a primitive type or void, then itsfinal
modifier is alwaystrue
and its interface modifier is alwaysfalse
. The values of its other modifiers are not determined by this specification.The modifier encodings are defined in The Java Virtual Machine Specification, table 4.1.
- Returns:
- the
int
representing the modifiers for this class - Since:
- JDK1.1
- See Also:
Modifier
-
getSigners
public Object[] 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 object represents a primitive type or void.
- Since:
- JDK1.1
-
getEnclosingMethod
public Method getEnclosingMethod()
If thisClass
object represents a local or anonymous class within a method, returns aMethod
object representing the immediately enclosing method of the underlying class. Returnsnull
otherwise. In particular, this method returnsnull
if the underlying class is a local or anonymous class immediately enclosed by a type 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
. - Since:
- 1.5
-
getEnclosingConstructor
public Constructor<?> getEnclosingConstructor()
If thisClass
object represents a local or anonymous class within a constructor, returns aConstructor
object representing the immediately enclosing constructor of the underlying class. Returnsnull
otherwise. In particular, this method returnsnull
if the underlying class is a local or anonymous class immediately enclosed by a type 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
. - Since:
- 1.5
-
getDeclaringClass
public Class<?> getDeclaringClass()
If the class or interface represented by thisClass
object is a member of another class, returns theClass
object 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 thisClass
object represents an array class, a primitive type, or void,then this method returns null.- Returns:
- the declaring class for this class
- Since:
- JDK1.1
-
getEnclosingClass
public Class<?> 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
- Since:
- 1.5
-
getSimpleName
public String getSimpleName()
Returns the simple name of the underlying class as given in the source code. Returns an empty string if the underlying class is anonymous.The simple name of an array is the simple name of the component type with "[]" appended. In particular the simple name of an array whose component type is anonymous is "[]".
- Returns:
- the simple name of the underlying class
- Since:
- 1.5
-
getCanonicalName
public String getCanonicalName()
Returns the canonical name of the underlying class as defined by the Java Language Specification. Returns null if the underlying class does not have a canonical name (i.e., if it is a local or anonymous class or an array whose component type does not have a canonical name).- Returns:
- the canonical name of the underlying class if it exists, and
null
otherwise. - Since:
- 1.5
-
isAnonymousClass
public boolean isAnonymousClass()
Returnstrue
if and only if the underlying class is an anonymous class.- Returns:
true
if and only if this class is an anonymous class.- Since:
- 1.5
-
isLocalClass
public boolean isLocalClass()
Returnstrue
if and only if the underlying class is a local class.- Returns:
true
if and only if this class is a local class.- Since:
- 1.5
-
isMemberClass
public boolean isMemberClass()
Returnstrue
if and only if the underlying class is a member class.- Returns:
true
if and only if this class is a member class.- Since:
- 1.5
-
getClasses
public Class<?>[] getClasses()
Returns an array containingClass
objects representing all the public classes and interfaces that are members of the class represented by thisClass
object. 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 thisClass
object has no public member classes or interfaces. This method also returns an array of length 0 if thisClass
object represents a primitive type, an array class, or void.- Returns:
- the array of
Class
objects representing the public members of this class - Throws:
SecurityException
- If a security manager, s, is present and any of the following conditions is met:- invocation of
s.checkMemberAccess(this, Member.PUBLIC)
method denies access to the 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
- invocation of
- Since:
- JDK1.1
-
getFields
public Field[] getFields() throws SecurityException
Returns an array containingField
objects reflecting all the accessible public fields of the class or interface represented by thisClass
object. The elements in the array returned are not sorted and are not in any particular order. This method returns an array of length 0 if the class or interface has no accessible public fields, or if it represents an array class, a primitive type, or void.Specifically, if this
Class
object represents a class, this method returns the public fields of this class and of all its superclasses. If thisClass
object represents an interface, this method returns the fields of this interface and of all its superinterfaces.The implicit length field for array class is not reflected by this method. User code should use the methods of class
Array
to manipulate arrays.See The Java Language Specification, sections 8.2 and 8.3.
- Returns:
- the array of
Field
objects representing the public fields - Throws:
SecurityException
- If a security manager, s, is present and any of the following conditions is met:- invocation of
s.checkMemberAccess(this, Member.PUBLIC)
denies access to the 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
- invocation of
- Since:
- JDK1.1
-
getMethods
public Method[] getMethods() throws SecurityException
Returns an array containingMethod
objects reflecting all the public member methods of the class or interface represented by thisClass
object, including those declared by the class or interface and those inherited from superclasses and superinterfaces. Array classes return all the (public) member methods inherited from theObject
class. The elements in the array returned are not sorted and are not in any particular order. This method returns an array of length 0 if thisClass
object represents a class or interface that has no public member methods, or if thisClass
object represents a primitive type or void.The class initialization method
<clinit>
is not included in the returned array. If the class declares multiple public member methods with the same parameter types, they are all included in the returned array.See The Java Language Specification, sections 8.2 and 8.4.
- Returns:
- the array of
Method
objects representing the public methods of this class - Throws:
SecurityException
- If a security manager, s, is present and any of the following conditions is met:- invocation of
s.checkMemberAccess(this, Member.PUBLIC)
denies access to the 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
- invocation of
- Since:
- JDK1.1
-
getConstructors
public Constructor<?>[] getConstructors() throws SecurityException
Returns an array containingConstructor
objects reflecting all the public constructors of the class represented by thisClass
object. 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. Note that while this method returns an array ofConstructor<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 holdConstructor
objects for different classes, which would violate the type guarantees ofConstructor<T>[]
.- Returns:
- the array of
Constructor
objects representing the public constructors of this class - Throws:
SecurityException
- If a security manager, s, is present and any of the following conditions is met:- invocation of
s.checkMemberAccess(this, Member.PUBLIC)
denies access to the 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
- invocation of
- Since:
- JDK1.1
-
getField
public Field getField(String name) throws NoSuchFieldException, SecurityException
Returns aField
object that reflects the specified public member field of the class or interface represented by thisClass
object. Thename
parameter is aString
specifying the simple name of the desired field.The field to be reflected is determined by the algorithm that follows. Let C be the class represented by this object:
- 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
NoSuchFieldException
is thrown.
See The Java Language Specification, sections 8.2 and 8.3.
- Parameters:
name
- the field name- Returns:
- the
Field
object of this class specified byname
- Throws:
NoSuchFieldException
- if a field with the specified name is not found.NullPointerException
- ifname
isnull
SecurityException
- If a security manager, s, is present and any of the following conditions is met:- invocation of
s.checkMemberAccess(this, Member.PUBLIC)
denies access to the 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
- invocation of
- Since:
- JDK1.1
-
getMethod
public Method getMethod(String name, Class<?>... parameterTypes) throws NoSuchMethodException, SecurityException
Returns aMethod
object that reflects the specified public member method of the class or interface represented by thisClass
object. Thename
parameter is aString
specifying the simple name of the desired method. TheparameterTypes
parameter is an array ofClass
objects that identify the method's formal parameter types, in declared order. IfparameterTypes
isnull
, it is treated as if it were an empty array.If the
name
is "<init>
;"or "<clinit>
" aNoSuchMethodException
is raised. Otherwise, the method to be reflected is determined by the algorithm that follows. Let C be the class represented by this object:- C is searched for any matching methods. If no matching method is found, the algorithm of step 1 is invoked recursively on the superclass of C.
- If no method was found in step 1 above, the superinterfaces of C are searched for a matching method. If any such method is found, it is reflected.
Note that there may be more than one matching method 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 method being overridden would have the same signature but different return types.
See The Java Language Specification, sections 8.2 and 8.4.
- Parameters:
name
- the name of the methodparameterTypes
- the list of parameters- Returns:
- the
Method
object that matches the specifiedname
andparameterTypes
- Throws:
NoSuchMethodException
- if a matching method is not found or if the name is "<init>"or "<clinit>".NullPointerException
- ifname
isnull
SecurityException
- If a security manager, s, is present and any of the following conditions is met:- invocation of
s.checkMemberAccess(this, Member.PUBLIC)
denies access to the 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
- invocation of
- Since:
- JDK1.1
-
getConstructor
public Constructor<T> getConstructor(Class<?>... parameterTypes) throws NoSuchMethodException, SecurityException
Returns aConstructor
object that reflects the specified public constructor of the class represented by thisClass
object. TheparameterTypes
parameter is an array ofClass
objects that identify the constructor's formal parameter types, in declared order. If thisClass
object 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
Class
object whose formal parameter types match those specified byparameterTypes
.- Parameters:
parameterTypes
- the parameter array- Returns:
- the
Constructor
object 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 any of the following conditions is met:- invocation of
s.checkMemberAccess(this, Member.PUBLIC)
denies access to the 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
- invocation of
- Since:
- JDK1.1
-
getDeclaredClasses
public Class<?>[] getDeclaredClasses() throws SecurityException
Returns an array ofClass
objects reflecting all the classes and interfaces declared as members of the class represented by thisClass
object. 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 thisClass
object represents a primitive type, an array class, or void.- Returns:
- the array of
Class
objects 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:- invocation of
s.checkMemberAccess(this, Member.DECLARED)
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
- invocation of
- Since:
- JDK1.1
-
getDeclaredFields
public Field[] getDeclaredFields() throws SecurityException
Returns an array ofField
objects reflecting all the fields declared by the class or interface represented by thisClass
object. This includes public, protected, default (package) access, and private fields, but excludes inherited fields. The elements in the array returned are not sorted and are not in any particular order. This method returns an array of length 0 if the class or interface declares no fields, or if thisClass
object represents a primitive type, an array class, or void.See The Java Language Specification, sections 8.2 and 8.3.
- Returns:
- the array of
Field
objects 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:- invocation of
s.checkMemberAccess(this, Member.DECLARED)
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
- invocation of
- Since:
- JDK1.1
-
getDeclaredMethods
public Method[] getDeclaredMethods() throws SecurityException
Returns an array ofMethod
objects reflecting all the methods declared by the class or interface represented by thisClass
object. This includes public, protected, default (package) access, and private methods, but excludes inherited methods. The elements in the array returned are not sorted and are not in any particular order. This method returns an array of length 0 if the class or interface declares no methods, or if thisClass
object represents a primitive type, an array class, or void. The class initialization method<clinit>
is not included in the returned array. If the class declares multiple public member methods with the same parameter types, they are all included in the returned array.See The Java Language Specification, section 8.2.
- Returns:
- the array of
Method
objects 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:- invocation of
s.checkMemberAccess(this, Member.DECLARED)
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
- invocation of
- Since:
- JDK1.1
-
getDeclaredConstructors
public Constructor<?>[] getDeclaredConstructors() throws SecurityException
Returns an array ofConstructor
objects reflecting all the constructors declared by the class represented by thisClass
object. 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 thisClass
object represents an interface, a primitive type, an array class, or void.See The Java Language Specification, section 8.2.
- Returns:
- the array of
Constructor
objects 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:- invocation of
s.checkMemberAccess(this, Member.DECLARED)
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
- invocation of
- Since:
- JDK1.1
-
getDeclaredField
public Field getDeclaredField(String name) throws NoSuchFieldException, SecurityException
Returns aField
object that reflects the specified declared field of the class or interface represented by thisClass
object. Thename
parameter is aString
that specifies the simple name of the desired field. Note that this method will not reflect thelength
field of an array class.- Parameters:
name
- the name of the field- Returns:
- the
Field
object for the specified field in this class - Throws:
NoSuchFieldException
- if a field with the specified name is not found.NullPointerException
- ifname
isnull
SecurityException
- If a security manager, s, is present and any of the following conditions is met:- invocation of
s.checkMemberAccess(this, Member.DECLARED)
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
- invocation of
- Since:
- JDK1.1
-
getDeclaredMethod
public Method getDeclaredMethod(String name, Class<?>... parameterTypes) throws NoSuchMethodException, SecurityException
Returns aMethod
object that reflects the specified declared method of the class or interface represented by thisClass
object. Thename
parameter is aString
that specifies the simple name of the desired method, and theparameterTypes
parameter is an array ofClass
objects 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>" aNoSuchMethodException
is raised.- Parameters:
name
- the name of the methodparameterTypes
- the parameter array- Returns:
- the
Method
object for the method of this class matching the specified name and parameters - Throws:
NoSuchMethodException
- if a matching method is not found.NullPointerException
- ifname
isnull
SecurityException
- If a security manager, s, is present and any of the following conditions is met:- invocation of
s.checkMemberAccess(this, Member.DECLARED)
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
- invocation of
- Since:
- JDK1.1
-
getDeclaredConstructor
public Constructor<T> getDeclaredConstructor(Class<?>... parameterTypes) throws NoSuchMethodException, SecurityException
Returns aConstructor
object that reflects the specified constructor of the class or interface represented by thisClass
object. TheparameterTypes
parameter is an array ofClass
objects that identify the constructor's formal parameter types, in declared order. If thisClass
object 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
Constructor
object 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:- invocation of
s.checkMemberAccess(this, Member.DECLARED)
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
- invocation of
- Since:
- JDK1.1
-
getResourceAsStream
public InputStream getResourceAsStream(String name)
Finds a resource with a given name. 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 object's class loader. If this object 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
name
begins with a'/'
('\u002f'), then the absolute name of the resource is the portion of thename
following the'/'
. - Otherwise, the absolute name is of the following form:
modified_package_name/name
Where the
modified_package_name
is the package name of this object with'/'
substituted for'.'
('\u002e').
- Parameters:
name
- name of the desired resource- Returns:
- A
InputStream
object ornull
if no resource with this name is found - Throws:
NullPointerException
- Ifname
isnull
- Since:
- JDK1.1
- If the
-
getResource
public URL getResource(String name)
Finds a resource with a given name. 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 object's class loader. If this object 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
name
begins with a'/'
('\u002f'), then the absolute name of the resource is the portion of thename
following the'/'
. - Otherwise, the absolute name is of the following form:
modified_package_name/name
Where the
modified_package_name
is the package name of this object with'/'
substituted for'.'
('\u002e').
- Parameters:
name
- name of the desired resource- Returns:
- A
URL
object ornull
if no resource with this name is found - Since:
- JDK1.1
- If the
-
getProtectionDomain
public ProtectionDomain getProtectionDomain()
Returns theProtectionDomain
of this class. If there is a security manager installed, this method first calls the security manager'scheckPermission
method 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 itscheckPermission
method doesn't allow getting the ProtectionDomain.- Since:
- 1.2
- See Also:
ProtectionDomain
,SecurityManager.checkPermission(java.security.Permission)
,RuntimePermission
-
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.Few programmers will have any need for this method; it is provided for the benefit of the JRE 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:
ClassLoader.setClassAssertionStatus(java.lang.String, boolean)
,ClassLoader.setPackageAssertionStatus(java.lang.String, boolean)
,ClassLoader.setDefaultAssertionStatus(boolean)
-
isEnum
public boolean isEnum()
Returns true if and only if this class was declared as an enum in the source code.- Returns:
- true if and only if this class was declared as an enum in the source code
- Since:
- 1.5
-
getEnumConstants
public T[] getEnumConstants()
Returns the elements of this enum class or null if this Class object does not represent an enum type.- Returns:
- an array containing the values comprising the enum class represented by this Class object in the order they're declared, or null if this Class object does not represent an enum type
- Since:
- 1.5
-
cast
public T cast(Object obj)
Casts an object to the class or interface represented by thisClass
object.- 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
public <U> Class<? extends U> asSubclass(Class<U> clazz)
Casts thisClass
object to represent a subclass of the class represented by the specified class object. Checks that that the cast is valid, and throws aClassCastException
if it is not. If this method succeeds, it always returns a reference to this class object.This method is useful when a client needs to "narrow" the type of a
Class
object to pass it to an API that restricts theClass
objects 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).- Returns:
- this
Class
object, cast to represent a subclass of the specified class object. - Throws:
ClassCastException
- if thisClass
object does not represent a subclass of the specified class (here "subclass" includes the class itself).- Since:
- 1.5
-
getAnnotation
public <A extends Annotation> A getAnnotation(Class<A> annotationClass)
Description copied from interface:AnnotatedElement
Returns this element's annotation for the specified type if such an annotation is present, else null.- Specified by:
getAnnotation
in interfaceAnnotatedElement
- 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
public boolean isAnnotationPresent(Class<? extends Annotation> annotationClass)
Description copied from interface:AnnotatedElement
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.- Specified by:
isAnnotationPresent
in 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
-
getAnnotations
public Annotation[] getAnnotations()
Description copied from interface:AnnotatedElement
Returns all annotations present on this element. (Returns an array of length zero if this element has no annotations.) The caller of this method is free to modify the returned array; it will have no effect on the arrays returned to other callers.- Specified by:
getAnnotations
in interfaceAnnotatedElement
- Returns:
- all annotations present on this element
- Since:
- 1.5
-
getDeclaredAnnotations
public Annotation[] getDeclaredAnnotations()
Description copied from interface:AnnotatedElement
Returns all annotations that are directly present on this element. Unlike the other methods in this interface, this method ignores inherited annotations. (Returns an array of length zero if no annotations are directly present on this element.) The caller of this method is free to modify the returned array; it will have no effect on the arrays returned to other callers.- Specified by:
getDeclaredAnnotations
in interfaceAnnotatedElement
- Returns:
- All annotations directly present on this element
- Since:
- 1.5
-
-
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