Class (Java Platform SE 7 )
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Class Class&T&
java.lang.Class&T&
Type Parameters:T - the type of the class modeled by this Class
For example, the type of String.class is Class&String&.
Use Class&?& if the class being modeled is
All Implemented Interfaces:
public final class Class&T&
implements , , ,
Instances of the class Class 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 a Class object
that is shared by all arrays with the same element type and number
of dimensions.
The primitive Java types (boolean,
byte, char, short,
int, long, float, and
double), and the keyword void are also
represented as Class objects.
Class has no public constructor. Instead Class
objects are constructed automatically by the Java Virtual Machine as classes
are loaded and by calls to the defineClass method in the class
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());
See Also:,
Method Summary
Modifier and Type
Method and Description
&U&&&? extends U&
(&U&&clazz)
Casts this Class object to represent a subclass of the class
represented by the specified class object.
Casts an object to the class or interface represented
by this Class object.
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 &?&
(&className)
Returns the Class object associated with the class or
interface with the given string name.
static &?&
boolean&initialize,
Returns the Class object associated with the class or
interface with the given string name, using the given class loader.
&A extends &&A
(&A&&annotationClass)
Returns this element's annotation for the specified type if
such an annotation is present, else null.
Returns all annotations present on this element.
Returns the canonical name of the underlying class as
defined by the Java Language Specification.
Returns an array containing Class objects representing all
the public classes and interfaces that are members of the class
represented by this Class object.
Returns the class loader for the class.
Returns the Class representing the component type of an
(&?&...&parameterTypes)
Returns a Constructor object that reflects the specified
public constructor of the class represented by this Class
Returns an array containing Constructor objects reflecting
all the public constructors of the class represented by this
Class object.
Returns all annotations that are directly present on this
Returns an array of Class objects reflecting all the
classes and interfaces declared as members of the class represented by
this Class object.
(&?&...&parameterTypes)
Returns a Constructor object that reflects the specified
constructor of the class or interface represented by this
Class object.
Returns an array of Constructor objects reflecting all the
constructors declared by the class represented by this
Class object.
Returns a Field object that reflects the specified declared
field of the class or interface represented by this Class
Returns an array of Field objects reflecting all the fields
declared by the class or interface represented by this
Class object.
&?&...&parameterTypes)
Returns a Method object that reflects the specified
declared method of the class or interface represented by this
Class object.
Returns an array of Method objects reflecting all the
methods declared by the class or interface represented by this
Class object.
If the class or interface represented by this Class object
is a member of another class, returns the Class object
representing the class in which it was declared.
Returns the immediately enclosing class of the underlying
If this Class object represents a local or anonymous
class within a constructor, returns a
object representing
the immediately enclosing constructor of the underlying
If this Class object represents a local or anonymous
class within a method, returns a
object representing the
immediately enclosing method of the underlying class.
Returns the elements of this enum class or null if this
Class object does not represent an enum type.
Returns a Field object that reflects the specified public
member field of the class or interface represented by this
Class object.
Returns an array containing Field objects reflecting all
the accessible public fields of the class or interface represented by
this Class object.
Returns the Types representing the interfaces
directly implemented by the class or interface represented by
this object.
Returns the Type representing the direct superclass of
the entity (class, interface, primitive type or void) represented by
this Class.
Determines the interfaces implemented by the class or interface
represented by this object.
&?&...&parameterTypes)
Returns a Method object that reflects the specified public
member method of the class or interface represented by this
Class object.
Returns an array containing Method objects reflecting all
the public member methods of the class or interface represented
by this Class object, including those declared by the class
or interface and those inherited from superclasses and
superinterfaces.
Returns the Java language modifiers for this class or interface, encoded
in an integer.
Returns the
name of the entity (class, interface, array class,
primitive type, or void) represented by this Class object,
as a String.
Gets the package for this class.
Returns the ProtectionDomain of this class.
Finds a resource with a given name.
Finds a resource with a given name.
Gets the signers of this class.
Returns the simple name of the underlying class as given in the
source code.
&? super &
Returns the Class representing the superclass of the entity
(class, interface, primitive type or void) represented by this
Returns an array of TypeVariable objects that represent the
type variables declared by the generic declaration represented by this
GenericDeclaration object, in declaration order.
Returns true if this Class object represents an annotation
(&? extends &&annotationClass)
Returns true if an annotation for the specified type
is present on this element, else false.
Returns true if and only if the underlying class
is an anonymous class.
Determines if this Class object represents an array class.
Determines if the class or interface represented by this
Class object is either the same as, or is a superclass or
superinterface of, the class or interface represented by the specified
Class parameter.
Returns true if and only if this class was declared as an enum in the
source code.
Determines if the specified Object is assignment-compatible
with the object represented by this Class.
Determines if the specified Class object represents an
interface type.
Returns true if and only if the underlying class
is a local class.
Returns true if and only if the underlying class
is a member class.
Determines if the specified Class object represents a
primitive type.
Returns true if this class
returns false otherwise.
Creates a new instance of the class represented by this Class
Converts the object to a string.
Methods inherited from class&java.lang.
, , , , , , , , ,
Method Detail
public&&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 by
If this Class object represents a
primitive type, this method returns the name of the primitive type.
this Class object represents void this method returns
Overrides:
&in class&
Returns:a string representation of this class object.
public static&&?&&forName(&className)
Returns the Class object associated with the class or
interface with the given string name.
Invoking this method is
equivalent to:
Class.forName(className, true, currentLoader)
where currentLoader denotes the defining class loader of
the current class.
For example, the following code fragment returns the
runtime Class descriptor for the class named
java.lang.Thread:
Class t = Class.forName("java.lang.Thread")
A call to forName("X") causes the class named
X to be initialized.
Parameters:className - the fully qualified name of the desired class.
Returns:the Class object for the class with the
specified name.
- if the linkage fails
- if the initialization provoked
by this method fails
- if the class cannot be located
public static&&?&&forName(&name,
boolean&initialize,
Returns the Class 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 by getName) 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 parameter
loader is null, the class is loaded through the bootstrap
class loader.
The class is initialized only if the
initialize parameter is true 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 is name. Therefore, this method cannot be used to
obtain any of the Class 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")
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 of The
Java Language Specification.
Note that this method does not check whether the requested class
is accessible to its caller.
If the loader is null, and a security
manager is present, and the caller's class loader is not null, then this
method calls the security manager's checkPermission method
with a RuntimePermission("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
- if the linkage fails
- if the initialization provoked
by this method fails
- if the class cannot be located by
the specified class loaderSince:
See Also:,
newInstance
public&&newInstance()
Creates a new instance of the class represented by this Class
The class is instantiated as if by a new
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.
this method effectively bypasses the compile-time exception
checking that would otherwise be performed by the compiler.
method avoids this problem by wrapping
any exception thrown by the constructor in a (checked) .
Returns:a newly allocated instance of the class represented by this
- if the class or its nullary
constructor is not accessible.
- if this Class represents an abstract class,
an interface, an array class, a primitive type,
or if the class has no
or if the instantiation fails for some other reason.
- if the initialization
provoked by this method fails.
- If a security manager, s, is present and any of the
following conditions is met:
invocation of
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
denies access to the package
of this class
isInstance
public&boolean&isInstance(&obj)
Determines if the specified Object is assignment-compatible
with the object represented by this Class.
This method is
the dynamic equivalent of the Java language instanceof
operator. The method returns true if the specified
Object argument is non-null and can be cast to the
reference type represented by this Class object without
raising a ClassCastException. It returns false
otherwise.
Specifically, if this Class object represents a
declared class, this method returns true if the specified
Object argument is an instance of the represented class (or
of any of its subclasses); it returns false otherwise. If
this Class object represents an array class, this method
returns true if the specified Object argument
can be converted to an object of the array class by an identity
conversion or by a widening
it returns
false otherwise. If this Class object
represents an interface, this method returns true if the
class or any superclass of the specified Object argument
imple it returns false otherwise. If
this Class object represents a primitive type, this method
returns false.
Parameters:obj - the object to check
Returns:true if obj is an instance of this classSince:
isAssignableFrom
public&boolean&isAssignableFrom(&?&&cls)
Determines if the class or interface represented by this
Class object is either the same as, or is a superclass or
superinterface of, the class or interface represented by the specified
Class parameter. It returns true
otherwise it returns false. If this Class
object represents a primitive type, this method returns
true if the specified Class parameter is
exactly this Class otherwise it returns
Specifically, this method tests whether the type represented by the
specified Class parameter can be converted to the type
represented by this Class 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 - the Class object to be checked
Returns:the boolean value indicating whether objects of the
type cls can be assigned to objects of this class
- if the specified Class parameter is
null.Since:
isInterface
public&boolean&isInterface()
Determines if the specified Class object represents an
interface type.
Returns:true if this object rep
false otherwise.
public&boolean&isArray()
Determines if this Class object represents an array class.
Returns:true if this object repre
false otherwise.Since:
isPrimitive
public&boolean&isPrimitive()
Determines if the specified Class 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, namely boolean, byte,
char, short, int,
long, float, and double.
These objects may only be accessed via the following public static
final variables, and are the only Class objects for which
this method returns true.
Returns:true if and only if this class represents a primitive typeSince:
See Also:,
isAnnotation
public&boolean&isAnnotation()
Returns true if this Class object represents an annotation
Note that if this method returns true,
would also return true, as all annotation types are also interfaces.
Returns:true if this class object represents an annotation
false otherwiseSince:
isSynthetic
public&boolean&isSynthetic()
Returns true if this class
returns false otherwise.
Returns:true if and only if this class is a synthetic class as
defined by the Java Language Specification.Since:
public&&getName()
Returns the
name of the entity (class, interface, array class,
primitive type, or void) represented by this Class object,
as a String.
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
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
The encoding of element type names is as follows:
Element Type
class or interface
Lclassname;
The class or interface name classname is the binary name of
the class specified above.
String.class.getName()
returns "java.lang.String"
byte.class.getName()
returns "byte"
(new Object[3]).getClass().getName()
returns "[Ljava.lang.O"
(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&&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 a RuntimePermission("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.
- if a security manager exists and its
checkPermission method denies
access to the class loader for the class.See Also:,
getTypeParameters
public&&&&&[]&getTypeParameters()
Returns an array of TypeVariable objects that represent the
type variables declared by the generic declaration represented by this
GenericDeclaration object, in declaration order.
Returns an
array of length 0 if the underlying generic declaration declares no type
variables.
Specified by:
&in interface&
Returns:an array of TypeVariable objects that represent
the type variables declared by this generic declaration
- if the generic
signature of this generic declaration does not conform to
the format specified in
The Java& Virtual Machine SpecificationSince:
getSuperclass
public&&? super &&getSuperclass()
Returns the Class representing the superclass of the entity
(class, interface, primitive type or void) represented by this
If this Class represents either the
Object class, an interface, a primitive type, or void, then
null is returned.
If this object represents an array class then the
Class object representing the Object class is
Returns:the superclass of the class represented by this object.
getGenericSuperclass
public&&getGenericSuperclass()
Returns the Type representing the direct superclass of
the entity (class, interface, primitive type or void) represented by
this Class.
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 of
semantics of the creation process for parameterized types.
this Class represents either the Object
class, an interface, a primitive type, or void, then null is
If this object represents an array class then the
Class object representing the Object class is
Returns:the superclass of the class represented by this object
- if the generic
class signature does not conform to the format specified in
The Java& Virtual Machine Specification
- if the generic superclass
refers to a non-existent type declaration
generic superclass refers to a parameterized type that cannot be
instantiated
for any reasonSince:
getPackage
public&&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&&?&[]&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 { ... }
suppose the value of s is an instance of
Shimmer; the value of the expression:
s.getClass().getInterfaces()[0]
is the Class object that represents interface
FloorWax; and the value of:
s.getClass().getInterfaces()[1]
is the Class object that represents interface
DessertTopping.
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&[]&getGenericInterfaces()
Returns the Types 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 of
for the semantics of the creation process for parameterized
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
interfaces Cloneable and Serializable 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
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
- if the generic class signature does not conform to the format
specified in
The Java& Virtual Machine Specification
- if any of the generic
superinterfaces refers to a non-existent type declaration
- if any of the generic superinterfaces refer to a parameterized
type that cannot be instantiated for any reasonSince:
getComponentType
public&&?&&getComponentType()
Returns the Class representing the component type of an
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 arraySince:
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 for public, protected,
private, final, static,
abstract and interface; they should be decoded
using the methods of class Modifier.
If the underlying class is an array class, then its
public, private and protected
modifiers are the same as those of its component type.
Class represents a primitive type or void, its
public modifier is always true, and its
protected and private modifiers are always
false. If this object represents an array class, a
primitive type or void, then its final modifier is always
true and its interface modifier is always
false. 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 classSince:
getSigners
public&[]&getSigners()
Gets the signers of this class.
Returns:the signers of this class, or null if there are no signers.
particular, this method returns null if this object represents
a primitive type or void.Since:
getEnclosingMethod
public&&getEnclosingMethod()
If this Class object represents a local or anonymous
class within a method, returns a
object representing the
immediately enclosing method of the underlying class. Returns
null otherwise.
In particular, this method returns null 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 loca otherwise null.Since:
getEnclosingConstructor
public&&?&&getEnclosingConstructor()
If this Class object represents a local or anonymous
class within a constructor, returns a
object representing
the immediately enclosing constructor of the underlying
class. Returns null otherwise.
In particular, this
method returns null 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 loca otherwise null.Since:
getDeclaringClass
public&&?&&getDeclaringClass()
If the class or interface represented by this Class object
is a member of another class, returns the Class 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.
this Class object represents an array class, a primitive
type, or void,then this method returns null.
Returns:the declaring class for this classSince:
getEnclosingClass
public&&?&&getEnclosingClass()
Returns the immediately enclosing class of the underlying
If the underlying class is a top level class this
method returns null.
Returns:the immediately enclosing class of the underlying classSince:
getSimpleName
public&&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 classSince:
getCanonicalName
public&&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:
isAnonymousClass
public&boolean&isAnonymousClass()
Returns true if and only if the underlying class
is an anonymous class.
Returns:true if and only if this class is an anonymous class.Since:
isLocalClass
public&boolean&isLocalClass()
Returns true if and only if the underlying class
is a local class.
Returns:true if and only if this class is a local class.Since:
isMemberClass
public&boolean&isMemberClass()
Returns true if and only if the underlying class
is a member class.
Returns:true if and only if this class is a member class.Since:
getClasses
public&&?&[]&getClasses()
Returns an array containing Class objects representing all
the public classes and interfaces that are members of the class
represented by this Class 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 this Class object has no public member
classes or interfaces.
This method also returns an array of length 0 if
this Class object represents a primitive type, an array
class, or void.
Returns:the array of Class objects representing the public
members of this class
- If a security manager, s, is present and any of the
following conditions is met:
invocation of
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
denies access to the package
of this class
public&[]&getFields()
Returns an array containing Field objects reflecting all
the accessible public fields of the class or interface represented by
this Class 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 this Class 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
- If a security manager, s, is present and any of the
following conditions is met:
invocation of
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
denies access to the package
of this class
getMethods
public&[]&getMethods()
Returns an array containing Method objects reflecting all
the public member methods of the class or interface represented
by this Class 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 the Object class.
The elements in the array
returned are not sorted and are not in any particular order.
method returns an array of length 0 if this Class object
represents a class or interface that has no public member methods, or if
this Class 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
- If a security manager, s, is present and any of the
following conditions is met:
invocation of
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
denies access to the package
of this class
getConstructors
public&&?&[]&getConstructors()
Returns an array containing Constructor objects reflecting
all the public constructors of the class represented by this
Class 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 of Constructor&T& objects (that is an array of constructors from
this class), the return type of this method is Constructor&?&[] and not Constructor&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 hold Constructor objects for
different classes, which would violate the type guarantees of
Constructor&T&[].
Returns:the array of Constructor objects representing the
public constructors of this class
- If a security manager, s, is present and any of the
following conditions is met:
invocation of
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
denies access to the package
of this class
public&&getField(&name)
Returns a Field object that reflects the specified public
member field of the class or interface represented by this
Class object. The name parameter is a
String specifying the simple name of the desired field.
The field to be reflected is determined by the algorithm that
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 by
- if a field with the specified name is
not found.
- if name is null
- If a security manager, s, is present and any of the
following conditions is met:
invocation of
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
denies access to the package
of this class
public&&getMethod(&name,
&?&...&parameterTypes)
Returns a Method object that reflects the specified public
member method of the class or interface represented by this
Class object. The name parameter is a
String specifying the simple name of the desired method. The
parameterTypes parameter is an array of Class
objects that identify the method's formal parameter types, in declared
order. If parameterTypes is null, it is
treated as if it were an empty array.
If the name is "&init&;"or "&clinit&" a
NoSuchMethodException 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.
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
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.
increased flexibility in the virtual machine can be used to
implement various language features.
For example, covariant
returns can
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 specified
name and parameterTypes
- if a matching method is not found
or if the name is "&init&"or "&clinit&".
- if name is null
- If a security manager, s, is present and any of the
following conditions is met:
invocation of
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
denies access to the package
of this class
getConstructor
public&&&&getConstructor(&?&...&parameterTypes)
Returns a Constructor object that reflects the specified
public constructor of the class represented by this Class
object. The parameterTypes parameter is an array of
Class objects that identify the constructor's formal
parameter types, in declared order.
If this Class 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 by parameterTypes.
Parameters:parameterTypes - the parameter array
Returns:the Constructor object of the public constructor that
matches the specified parameterTypes
- if a matching method is not found.
- If a security manager, s, is present and any of the
following conditions is met:
invocation of
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
denies access to the package
of this class
getDeclaredClasses
public&&?&[]&getDeclaredClasses()
Returns an array of Class objects reflecting all the
classes and interfaces declared as members of the class represented by
this Class 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 this Class object represents a
primitive type, an array class, or void.
Returns:the array of Class objects representing all the
declared members of this class
- If a security manager, s, is present and any of the
following conditions is met:
invocation of
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
denies access to the package
of this class
getDeclaredFields
public&[]&getDeclaredFields()
Returns an array of Field objects reflecting all the fields
declared by the class or interface represented by this
Class 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 this Class 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
- If a security manager, s, is present and any of the
following conditions is met:
invocation of
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
denies access to the package
of this class
getDeclaredMethods
public&[]&getDeclaredMethods()
Returns an array of Method objects reflecting all the
methods declared by the class or interface represented by this
Class 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 this Class object
represents a primitive type, an array class, or void.
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
See The Java Language Specification, section 8.2.
Returns:the array of Method objects representing all the
declared methods of this class
- If a security manager, s, is present and any of the
following conditions is met:
invocation of
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
denies access to the package
of this class
getDeclaredConstructors
public&&?&[]&getDeclaredConstructors()
Returns an array of Constructor objects reflecting all the
constructors declared by the class represented by this
Class 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.
class has a default constructor, it is included in the returned array.
This method returns an array of length 0 if this Class
object represents an interface, a primitive type, an array class, or
See The Java Language Specification, section 8.2.
Returns:the array of Constructor objects representing all the
declared constructors of this class
- If a security manager, s, is present and any of the
following conditions is met:
invocation of
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
denies access to the package
of this class
getDeclaredField
public&&getDeclaredField(&name)
Returns a Field object that reflects the specified declared
field of the class or interface represented by this Class
object. The name parameter is a String that
specifies the simple name of the desired field.
Note that this method
will not reflect the length field of an array class.
Parameters:name - the name of the field
Returns:the Field object for the specified field in this
- if a field with the specified name is
not found.
- if name is null
- If a security manager, s, is present and any of the
following conditions is met:
invocation of
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
denies access to the package
of this class
getDeclaredMethod
public&&getDeclaredMethod(&name,
&?&...&parameterTypes)
Returns a Method object that reflects the specified
declared method of the class or interface represented by this
Class object. The name parameter is a
String that specifies the simple name of the desired
method, and the parameterTypes parameter is an array of
Class 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
otherwise one of the methods is chosen arbitrarily.
name is "&init&"or "&clinit&" a NoSuchMethodException
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
- if a matching method is not found.
- if name is null
- If a security manager, s, is present and any of the
following conditions is met:
invocation of
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
denies access to the package
of this class
getDeclaredConstructor
public&&&&getDeclaredConstructor(&?&...&parameterTypes)
Returns a Constructor object that reflects the specified
constructor of the class or interface represented by this
Class object.
The parameterTypes parameter is
an array of Class objects that identify the constructor's
formal parameter types, in declared order.
If this Class 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
- if a matching method is not found.
- If a security manager, s, is present and any of the
following conditions is met:
invocation of
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
denies access to the package
of this class
getResourceAsStream
public&&getResourceAsStream(&name)
Finds a resource with a given name.
The rules for searching resources
associated with a given class are implemented by the defining
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 to .
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 the name 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
object or null if
no resource with this name is found
- If name is nullSince:
getResource
public&&getResource(&name)
Finds a resource with a given name.
The rules for searching resources
associated with a given class are implemented by the defining
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 to .
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 the name 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
object or null if no
resource with this name is foundSince:
getProtectionDomain
public&&getProtectionDomain()
Returns the ProtectionDomain of this class.
If there is a
security manager installed, this method first calls the security
manager's checkPermission method with a
RuntimePermission("getProtectionDomain") permission to
ensure it's ok to get the
ProtectionDomain.
Returns:the ProtectionDomain of this class
- if a security manager exists and its
checkPermission method doesn't allow
getting the ProtectionDomain.Since:
See Also:,
desiredAssertionStatus
public&boolean&desiredAssertionStatus()
Returns the assertion status that would be assigned to this
class if it were to be initialized at the time this method is invoked.
If this class has had its assertion status set, the most recent
sett otherwise, if any package default assertion
status pertains to this class, the most recent setting for the most
specific pertinent package default assertio
otherwise, if this class is not a system class (i.e., it has a
class loader) its class loader's default assertio
otherwise, the system class default assertion status is returned.
Few programmers will have any
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:
See Also:,
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 codeSince:
getEnumConstants
public&[]&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 typeSince:
public&&cast(&obj)
Casts an object to the class or interface represented
by this Class object.
Parameters:obj - the object to be cast
Returns:the object after casting, or null if obj is null
- if the object is not
null and is not assignable to the type T.Since:
asSubclass
public&&U&&&? extends U&&asSubclass(&U&&clazz)
Casts this Class object to represent a subclass of the class
represented by the specified class object.
Checks that that the cast
is valid, and throws a ClassCastException if it is not.
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 the
Class 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.
- if this Class object does not
represent a subclass of the specified class (here "subclass" includes
the class itself).Since:
getAnnotation
public&&A extends &&A&getAnnotation(&A&&annotationClass)
Description copied from interface:&
Returns this element's annotation for the specified type if
such an annotation is present, else null.
Specified by:
&in interface&
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
- if the given annotation class is nullSince:
isAnnotationPresent
public&boolean&isAnnotationPresent(&? extends &&annotationClass)
Description copied from interface:&
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:
&in interface&
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
- if the given annotation class is nullSince:
getAnnotations
public&[]&getAnnotations()
Description copied from interface:&
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 modif it will have no
effect on the arrays returned to other callers.
Specified by:
&in interface&
Returns:all annotations present on this elementSince:
getDeclaredAnnotations
public&[]&getDeclaredAnnotations()
Description copied from interface:&
Returns all annotations that are directly present on this
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 modif it will have no
effect on the arrays returned to other callers.
Specified by:
&in interface&
Returns:All annotations directly present on this elementSince:
For further API reference and developer documentation, see . That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.
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