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Class Class<T>

java.lang.Objectjava.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 classClass<T>
extendsObject
implementsSerializable,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 aClass 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 theClass object for a named type (or for void) using a class literal (JLS Section15.8.2). 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

toString

publicStringtoString()

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".

Overrides:

toString in classObject

Returns:

a string representation of this class object.

forName

public staticClass<?>forName(String className)                        throwsClassNotFoundException

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)

wherecurrentLoader denotes the defining class loader of the current class.

For example, the following code fragment returns the runtimeClass descriptor for the class namedjava.lang.Thread:

   Class t = Class.forName("java.lang.Thread")

A call toforName("X") causes the class namedX to be initialized.

Parameters:

className - the fully qualified name of the desired class.

Returns:

theClass object for the class with the specified name.

Throws:

LinkageError - if the linkage fails

ExceptionInInitializerError - if the initialization provoked by this method fails

ClassNotFoundException - if the class cannot be located

forName

public staticClass<?>forName(String name,                               boolean initialize,ClassLoader loader)                        throwsClassNotFoundException

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.

Ifname 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.

Ifname 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")

is equivalent to:

  Class.forName("Foo", true, this.getClass().getClassLoader())

Note that this method throws errors related to loading, linking or initializing as specified in Sections 12.2, 12.3 and 12.4 ofThe Java Language Specification. Note that this method does not check whether the requested class is accessible to its caller.

If theloader 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 class

initialize - whether the class must be initialized

loader - class loader from which the class must be loaded

Returns:

class object representing the desired class

Throws:

LinkageError - if the linkage fails

ExceptionInInitializerError - if the initialization provoked by this method fails

ClassNotFoundException - if the class cannot be located by the specified class loader

Since:

1.2

See Also:

forName(String),ClassLoader

newInstance

publicTnewInstance()              throwsInstantiationException,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. TheConstructor.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 ofs.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 ofs.checkPackageAccess() denies access to the package of this class

isInstance

public booleanisInstance(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 thisClass 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 ifobj is an instance of this class

Since:

JDK1.1

isAssignableFrom

public booleanisAssignableFrom(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 specifiedClass parameter can be converted to the type represented by thisClass object via an identity conversion or via a widening reference conversion. SeeThe Java Language Specification, sections 5.1.1 and 5.1.4 , for details.

Parameters:

cls - theClass object to be checked

Returns:

theboolean 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 booleanisInterface()

Determines if the specifiedClass object represents an interface type.

Returns:

true if this object represents an interface;false otherwise.

isArray

public booleanisArray()

Determines if thisClass object represents an array class.

Returns:

true if this object represents an array class;false otherwise.

Since:

JDK1.1

isPrimitive

public booleanisPrimitive()

Determines if the specifiedClass object represents a primitive type.

There are nine predefinedClass 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 onlyClass 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 booleanisAnnotation()

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 booleanisSynthetic()

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

publicStringgetName()

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, Second Edition.

If this class object represents a primitive type or void, then the name returned is aString 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 nameclassname 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

publicClassLoadergetClassLoader()

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'scheckPermission 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

publicTypeVariable<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 ofTypeVariable 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, 3rd edition

Since:

1.5

getSuperclass

publicClass<? superT>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

publicTypegetGenericSuperclass()

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, theType 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 Specification, 3rd edition

TypeNotPresentException - if the generic superclass refers to a non-existent type declaration

MalformedParameterizedTypeException - if the generic superclass refers to a parameterized type that cannot be instantiated for any reason

Since:

1.5

getPackage

publicPackagegetPackage()

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

publicClass<?>[]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 theimplements clause of the declaration of the class represented by this object. For example, given the declaration:

 class Shimmer implements FloorWax, DessertTopping { ... }

suppose the value ofs is an instance ofShimmer; the value of the expression:

 s.getClass().getInterfaces()[0]

is theClass object that represents interfaceFloorWax; and the value of:

 s.getClass().getInterfaces()[1]

is theClass 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 theextends 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

publicType[]getGenericInterfaces()

Returns theTypes representing the interfaces directly implemented by the class or interface represented by this object.

If a superinterface is a parameterized type, theType 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 theimplements 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 theextends 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 Specification, 3rd edition

TypeNotPresentException - if any of the generic superinterfaces refers to a non-existent type declaration

MalformedParameterizedTypeException - if any of the generic superinterfaces refer to a parameterized type that cannot be instantiated for any reason

Since:

1.5

getComponentType

publicClass<?>getComponentType()

Returns theClass representing the component type of an array. If this class does not represent an array class this method returns null.

Returns:

theClass representing the component type of this class if this class is an array

Since:

JDK1.1

See Also:

Array

getModifiers

public intgetModifiers()

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 itspublic,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 inThe Java Virtual Machine Specification, table 4.1.

Returns:

theint representing the modifiers for this class

Since:

JDK1.1

See Also:

Modifier

getSigners

publicObject[]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

publicMethodgetEnclosingMethod()

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; otherwisenull.

Since:

1.5

getEnclosingConstructor

publicConstructor<?>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; otherwisenull.

Since:

1.5

getDeclaringClass

publicClass<?>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

publicClass<?>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

publicStringgetSimpleName()

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

publicStringgetCanonicalName()

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, andnull otherwise.

Since:

1.5

isAnonymousClass

public booleanisAnonymousClass()

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 booleanisLocalClass()

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 booleanisMemberClass()

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

publicClass<?>[]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 ofClass 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 ofs.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 ofs.checkPackageAccess() denies access to the package of this class

Since:

JDK1.1

getFields

publicField[]getFields()                  throwsSecurityException

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 thisClass 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 classArray to manipulate arrays.

SeeThe Java Language Specification, sections 8.2 and 8.3.

Returns:

the array ofField objects representing the public fields

Throws:

SecurityException - If a security manager,s, is present and any of the following conditions is met:

• invocation ofs.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 ofs.checkPackageAccess() denies access to the package of this class

Since:

JDK1.1

getMethods

publicMethod[]getMethods()                    throwsSecurityException

Returns an array containingMethod objects reflecting all the publicmember 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.

SeeThe Java Language Specification, sections 8.2 and 8.4.

Returns:

the array ofMethod 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 ofs.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 ofs.checkPackageAccess() denies access to the package of this class

Since:

JDK1.1

getConstructors

publicConstructor<?>[]getConstructors()                                 throwsSecurityException

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<?>[] andnotConstructor<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 ofConstructor 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 ofs.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 ofs.checkPackageAccess() denies access to the package of this class

Since:

JDK1.1

getField

publicFieldgetField(String name)               throwsNoSuchFieldException,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:

1. If C declares a public field with the name specified, that is the field to be reflected.
2. 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.
3. 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 aNoSuchFieldException is thrown.

SeeThe Java Language Specification, sections 8.2 and 8.3.

Parameters:

name - the field name

Returns:

theField 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 ofs.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 ofs.checkPackageAccess() denies access to the package of this class

Since:

JDK1.1

getMethod

publicMethodgetMethod(String name,Class<?>... parameterTypes)                 throwsNoSuchMethodException,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 thename 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:

1. C is searched for anymatching methods. If no matching method is found, the algorithm of step 1 is invoked recursively on the superclass of C.
2. 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.

To find a matching method in a class C:  If C declares exactly one public method with the specified name and exactly the same formal parameter types, that is the method reflected. If more than one such method is found in C, and one of these methods has a return type that is more specific than any of the others, that method is reflected; otherwise one of the methods is chosen arbitrarily.

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 withbridge methods; the bridge method and the method being overridden would have the same signature but different return types.

SeeThe Java Language Specification, sections 8.2 and 8.4.

Parameters:

name - the name of the method

parameterTypes - the list of parameters

Returns:

theMethod 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 ofs.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 ofs.checkPackageAccess() denies access to the package of this class

Since:

JDK1.1

getConstructor

publicConstructor<T>getConstructor(Class<?>... parameterTypes)                              throwsNoSuchMethodException,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 thisClass object whose formal parameter types match those specified byparameterTypes.

Parameters:

parameterTypes - the parameter array

Returns:

theConstructor 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 ofs.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 ofs.checkPackageAccess() denies access to the package of this class

Since:

JDK1.1

getDeclaredClasses

publicClass<?>[]getDeclaredClasses()                              throwsSecurityException

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 ofClass 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 ofs.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 ofs.checkPackageAccess() denies access to the package of this class

Since:

JDK1.1

getDeclaredFields

publicField[]getDeclaredFields()                          throwsSecurityException

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.

SeeThe Java Language Specification, sections 8.2 and 8.3.

Returns:

the array ofField 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 ofs.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 ofs.checkPackageAccess() denies access to the package of this class

Since:

JDK1.1

getDeclaredMethods

publicMethod[]getDeclaredMethods()                            throwsSecurityException

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.

SeeThe Java Language Specification, section 8.2.

Returns:

the array ofMethod 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 ofs.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 ofs.checkPackageAccess() denies access to the package of this class

Since:

JDK1.1

getDeclaredConstructors

publicConstructor<?>[]getDeclaredConstructors()                                         throwsSecurityException

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.

SeeThe Java Language Specification, section 8.2.

Returns:

the array ofConstructor 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 ofs.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 ofs.checkPackageAccess() denies access to the package of this class

Since:

JDK1.1

getDeclaredField

publicFieldgetDeclaredField(String name)                       throwsNoSuchFieldException,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:

theField 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 ofs.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 ofs.checkPackageAccess() denies access to the package of this class

Since:

JDK1.1

getDeclaredMethod

publicMethodgetDeclaredMethod(String name,Class<?>... parameterTypes)                         throwsNoSuchMethodException,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 method

parameterTypes - the parameter array

Returns:

theMethod 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 ofs.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 ofs.checkPackageAccess() denies access to the package of this class

Since:

JDK1.1

getDeclaredConstructor

publicConstructor<T>getDeclaredConstructor(Class<?>... parameterTypes)                                      throwsNoSuchMethodException,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:

TheConstructor 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 ofs.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 ofs.checkPackageAccess() denies access to the package of this class

Since:

JDK1.1

getResourceAsStream

publicInputStreamgetResourceAsStream(String name)

Finds a resource with a given name. The rules for searching resources associated with a given class are implemented by the definingclass 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 thename 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 themodified_package_name is the package name of this object with'/' substituted for'.' ('\u002e').

Parameters:

name - name of the desired resource

Returns:

AInputStream object ornull if no resource with this name is found

Throws:

NullPointerException - Ifname isnull

Since:

JDK1.1

getResource

publicURLgetResource(String name)

Finds a resource with a given name. The rules for searching resources associated with a given class are implemented by the definingclass 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 thename 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 themodified_package_name is the package name of this object with'/' substituted for'.' ('\u002e').

Parameters:

name - name of the desired resource

Returns:

AURL object ornull if no resource with this name is found

Since:

JDK1.1

getProtectionDomain

publicProtectionDomaingetProtectionDomain()

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 booleandesiredAssertionStatus()

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 booleanisEnum()

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

publicT[]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

publicTcast(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 aClass 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:

thisClass 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 extendsAnnotation> AgetAnnotation(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 booleanisAnnotationPresent(Class<? extendsAnnotation> 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

publicAnnotation[]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

publicAnnotation[]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