T
- the type of the class modeled by this Class
object. For example, the type of String.class
is Class<String>
. Use Class<?>
if the class being modeled is
unknown.public final class Class<T> extends Object implements Serializable, GenericDeclaration, Type, AnnotatedElement
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
loader.
The following example uses a Class
object to print the
class name of an object:
void printClassName(Object obj) { System.out.println("The class of " + obj + " is " + obj.getClass().getName()); }
It is also possible to get the Class
object for a named
type (or for void) using a class literal. See Section 15.8.2 of
The Java™ Language Specification.
For example:
System.out.println("The name of class Foo is: "+Foo.class.getName());
ClassLoader.defineClass(byte[], int, int)
,
Serialized FormModifier and Type | Method and Description |
---|---|
<U> Class<? extends U> |
asSubclass(Class<U> clazz)
asSubclass casts this class to a subclass of this class.
|
T |
cast(Object obj)
cast casts a given object to this type.
|
boolean |
desiredAssertionStatus()
Returns the assertion status that would be assigned to this
class if it were to be initialized at the time this method is invoked.
|
static Class<?> |
forName(String className)
Returns the
Class object associated with the class or
interface with the given string name. |
static Class<?> |
forName(String name,
boolean initialize,
ClassLoader loader)
Returns the
Class object associated with the class or
interface with the given string name, using the given class loader. |
AnnotatedType[] |
getAnnotatedInterfaces()
Returns an array of
AnnotatedType objects that represent the use
of types to specify superinterfaces of the entity represented by this
Class object. |
AnnotatedType |
getAnnotatedSuperclass()
Returns an
AnnotatedType object that represents the use of a
type to specify the superclass of the entity represented by this Class object. |
<A extends Annotation> |
getAnnotation(Class<A> annotationClass)
Returns this element's annotation for the specified type if
such an annotation is present, else null.
|
Annotation[] |
getAnnotations()
Returns annotations that are present on this element.
|
<A extends Annotation> |
getAnnotationsByType(Class<A> annotationClass)
Returns annotations that are associated with this element.
|
String |
getCanonicalName()
Returns the canonical name of the underlying class as
defined by the Java Language Specification.
|
Class<?>[] |
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. |
ClassLoader |
getClassLoader()
Returns the class loader for the class.
|
Class<?> |
getComponentType()
getComponentType returns the element type of an array.
|
Constructor<T> |
getConstructor(Class<?>... parameterTypes)
Returns a
Constructor object that reflects the specified
public constructor of the class represented by this Class
object. |
Constructor<?>[] |
getConstructors()
Returns an array containing
Constructor objects reflecting
all the public constructors of the class represented by this
Class object. |
<A extends Annotation> |
getDeclaredAnnotation(Class<A> annotationClass)
Returns this element's annotation for the specified type if
such an annotation is directly present, else null.
|
Annotation[] |
getDeclaredAnnotations()
Returns annotations that are directly present on this element.
|
<A extends Annotation> |
getDeclaredAnnotationsByType(Class<A> annotationClass)
Returns this element's annotation(s) for the specified type if
such annotations are either directly present or
indirectly present.
|
Class<?>[] |
getDeclaredClasses()
Returns an array of
Class objects reflecting all the
classes and interfaces declared as members of the class represented by
this Class object. |
Constructor<T> |
getDeclaredConstructor(Class<?>... parameterTypes)
Returns a
Constructor object that reflects the specified
constructor of the class or interface represented by this
Class object. |
Constructor<?>[] |
getDeclaredConstructors()
Returns an array of
Constructor objects reflecting all the
constructors declared by the class represented by this
Class object. |
Field |
getDeclaredField(String name)
Returns a
Field object that reflects the specified declared
field of the class or interface represented by this Class
object. |
Field[] |
getDeclaredFields()
Returns an array of
Field objects reflecting all the fields
declared by the class or interface represented by this
Class object. |
Method |
getDeclaredMethod(String name,
Class<?>... parameterTypes)
Returns a
Method object that reflects the specified
declared method of the class or interface represented by this
Class object. |
Method[] |
getDeclaredMethods()
Returns an array containing
Method objects reflecting all the
declared methods of the class or interface represented by this Class object, including public, protected, default (package)
access, and private methods, but excluding inherited methods. |
Class<?> |
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. |
Class<?> |
getEnclosingClass()
Returns the immediately enclosing class of the underlying
class.
|
Constructor<?> |
getEnclosingConstructor()
If this
Class object represents a local or anonymous
class within a constructor, returns a Constructor object representing
the immediately enclosing constructor of the underlying
class. |
Method |
getEnclosingMethod()
If this
Class object represents a local or anonymous
class within a method, returns a Method object representing the
immediately enclosing method of the underlying class. |
T[] |
getEnumConstants()
Returns the elements of this enum class or null if this
Class object does not represent an enum type.
|
Field |
getField(String name)
Returns a
Field object that reflects the specified public member
field of the class or interface represented by this Class
object. |
Field[] |
getFields()
Returns an array containing
Field objects reflecting all
the accessible public fields of the class or interface represented by
this Class object. |
Type[] |
getGenericInterfaces()
Return array of interfaces implemented by this with actual
generic parameters
|
Type |
getGenericSuperclass()
Return super class including actual generic parameters.
|
Class[] |
getInterfaces()
getInterfaces returns an array of all the interface classes this
class implements directly.
|
Method |
getMethod(String name,
Class<?>... parameterTypes)
Returns a
Method object that reflects the specified public
member method of the class or interface represented by this
Class object. |
Method[] |
getMethods()
Returns an array containing
Method objects reflecting all the
public 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. |
int |
getModifiers()
getModifiers returns modifier set for this class
|
String |
getName()
getName returns the name of this class.
|
Package |
getPackage()
Gets the object representing the package which contains this
class.
|
ProtectionDomain |
getProtectionDomain()
Returns the
ProtectionDomain of this class. |
URL |
getResource(String name)
Finds a resource with a given name.
|
InputStream |
getResourceAsStream(String name)
Finds a resource with a given name.
|
Object[] |
getSigners()
getSigners returns the signers of this class, or null if there
are none or this is a primitive type.
|
String |
getSimpleName()
Returns the simple name of the underlying class as given in the
source code.
|
Class<? super T> |
getSuperclass()
getSuperclass gets the super class of this class
|
String |
getTypeName()
Return an informative string for the name of this type.
|
TypeVariable<Class<T>>[] |
getTypeParameters()
Return an array of the declared type parameters for a generic
class.
|
boolean |
isAnnotation()
check if this class instance represents an annotation.
|
boolean |
isAnnotationPresent(Class<? extends Annotation> annotationClass)
Returns true if an annotation for the specified type
is present on this element, else false.
|
boolean |
isAnonymousClass()
Returns
true if and only if the underlying class
is an anonymous class. |
boolean |
isArray()
Test if this class is an array.
|
boolean |
isAssignableFrom(Class<?> cls)
Checks if an object of type cls can be assigned to a variable of
this type.
|
boolean |
isEnum()
Returns true if and only if this class was declared as an enum in the
source code.
|
boolean |
isInstance(Object obj)
isInstance checks if "obj instanceof >>this<<" would result in
true, i.e., if this is a class, obj's class is equal to or a
subclass of this, otherwise if this is an interface, obj's class
implements the interface, otherwise if this is an array type,
obj's type is an array that is assignment compatible to this.
|
boolean |
isInterface()
Test if this class is an interface.
|
boolean |
isLocalClass()
Returns
true if and only if the underlying class
is a local class. |
boolean |
isMemberClass()
Returns
true if and only if the underlying class
is a member class. |
boolean |
isPrimitive()
Test if this class represents a primitive type, i.e., it is one of
the values Boolean.TYPE, Character.TYPE, Byte.TYPE, Short.TYPE,
Integer.TYPE, Long.TYPE, Float.TYPE, Double.TYPE, and Void.TYPE.
|
boolean |
isSynthetic()
check if this class instance represents a synthetic class
|
T |
newInstance()
Creates a new instance of the class represented by this
Class
object. |
String |
toGenericString()
Returns a string describing this
Class , including
information about modifiers and type parameters. |
String |
toString()
toString creates a string representation of this class
|
public Class<? super T> getSuperclass()
public String toString()
public String toGenericString()
Class
, including
information about modifiers and type parameters.
The string is formatted as a list of type modifiers, if any,
followed by the kind of type (empty string for primitive types
and class
, enum
, interface
, or
@
interface
, as appropriate), followed
by the type's name, followed by an angle-bracketed
comma-separated list of the type's type parameters, if any.
A space is used to separate modifiers from one another and to
separate any modifiers from the kind of type. The modifiers
occur in canonical order. If there are no type parameters, the
type parameter list is elided.
Note that since information about the runtime representation of a type is being generated, modifiers not present on the originating source code or illegal on the originating source code may be present.
Class
, including
information about modifiers and type parameterspublic static Class<?> forName(String className) throws ClassNotFoundException
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.
For JamaicaVM, this method is never called from compiled code, the compiler replaces a call forName(x) by forName(x,true,null) since the class loader of any statically compiled method is the system class loader.
className
- the fully qualified name of the desired class.Class
object for the class with the
specified name.LinkageError
- if the linkage failsExceptionInInitializerError
- if the initialization provoked
by this method failsClassNotFoundException
- if the class cannot be locatedpublic static Class<?> forName(String name, boolean initialize, ClassLoader loader) throws ClassNotFoundException
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.
name
- fully qualified name of the desired classinitialize
- if true
the class will be initialized.
See Section 12.4 of The Java Language Specification.loader
- class loader from which the class must be loadedLinkageError
- if the linkage failsExceptionInInitializerError
- if the initialization provoked
by this method failsClassNotFoundException
- if the class cannot be located by
the specified class loaderforName(String)
,
ClassLoader
public T newInstance() throws InstantiationException, IllegalAccessException
Class
object. 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. Use of
this method effectively bypasses the compile-time exception
checking that would otherwise be performed by the compiler.
The Constructor.newInstance
method avoids this problem by wrapping
any exception thrown by the constructor in a (checked) InvocationTargetException
.
IllegalAccessException
- if the class or its nullary
constructor is not accessible.InstantiationException
- if this Class
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
the caller's class loader is not the same as or an
ancestor of the class loader for the current class and
invocation of s.checkPackageAccess()
denies access to the package
of this class.public boolean isInstance(Object obj)
If this is a primitive type or obj is null, the result is false..
obj
- an object reference or null.public boolean isAssignableFrom(Class<?> cls)
The result is true iff this is a class and cls is equal to or a subclass of this, otherwise if this is an interface and cls is a class or an interface that is equal to or implements this, otherwise if this is an array type and cls is an array that is assignment compatible to this, else if this is a primitive type and cls is equal to this.
cls
- the source type of the assignmentNullPointerException
- is cls is nullpublic boolean isInterface()
public boolean isArray()
public boolean isPrimitive()
public String getName()
The resulting string is interned().
public ClassLoader getClassLoader()
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.
SecurityException
- if a security manager exists and its
checkPermission
method denies
access to the class loader for the class.ClassLoader
,
SecurityManager.checkPermission(java.security.Permission)
,
RuntimePermission
public Package getPackage()
public Class[] getInterfaces()
public Class<?> getComponentType()
public int getModifiers()
public Object[] getSigners()
public Class<?> getDeclaringClass() throws SecurityException
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. If
this Class
object represents an array class, a primitive
type, or void,then this method returns null.SecurityException
- If a security manager, s, is present and the caller's
class loader is not the same as or an ancestor of the class
loader for the declaring class and invocation of s.checkPackageAccess()
denies access to the package of the declaring classpublic Class<?>[] getClasses()
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.Class
objects representing the public
members of this classSecurityException
- If a security manager, s, is present and
the caller's class loader is not the same as or an
ancestor of the class loader for the current class and
invocation of s.checkPackageAccess()
denies access to the package
of this class.public Field[] getFields() throws SecurityException
Field
objects reflecting all
the accessible public fields of the class or interface represented by
this Class
object.
If this Class
object represents a class or interface with no
no accessible public fields, then this method returns an array of length
0.
If this Class
object represents a class, then this method
returns the public fields of the class and of all its superclasses.
If this Class
object represents an interface, then this
method returns the fields of the interface and of all its
superinterfaces.
If this Class
object represents an array type, a primitive
type, or void, then this method returns an array of length 0.
The elements in the returned array are not sorted and are not in any particular order.
Field
objects representing the
public fieldsSecurityException
- If a security manager, s, is present and
the caller's class loader is not the same as or an
ancestor of the class loader for the current class and
invocation of s.checkPackageAccess()
denies access to the package
of this class.public Method[] getMethods() throws SecurityException
Method
objects reflecting all the
public 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.
If this Class
object represents a type that has multiple
public methods with the same name and parameter types, but different
return types, then the returned array has a Method
object for
each such method.
If this Class
object represents a type with a class
initialization method <clinit>
, then the returned array does
not have a corresponding Method
object.
If this Class
object represents an array type, then the
returned array has a Method
object for each of the public
methods inherited by the array type from Object
. It does not
contain a Method
object for clone()
.
If this Class
object represents an interface then the
returned array does not contain any implicitly declared methods from
Object
. Therefore, if no methods are explicitly declared in
this interface or any of its superinterfaces then the returned array
has length 0. (Note that a Class
object which represents a class
always has public methods, inherited from Object
.)
If this Class
object represents a primitive type or void,
then the returned array has length 0.
Static methods declared in superinterfaces of the class or interface
represented by this Class
object are not considered members of
the class or interface.
The elements in the returned array are not sorted and are not in any particular order.
Method
objects representing the
public methods of this classSecurityException
- If a security manager, s, is present and
the caller's class loader is not the same as or an
ancestor of the class loader for the current class and
invocation of s.checkPackageAccess()
denies access to the package
of this class.public Constructor<?>[] getConstructors() throws SecurityException
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>[]
.Constructor
objects representing the
public constructors of this classSecurityException
- If a security manager, s, is present and
the caller's class loader is not the same as or an
ancestor of the class loader for the current class and
invocation of s.checkPackageAccess()
denies access to the package
of this class.public Field getField(String name) throws NoSuchFieldException, SecurityException
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 follows. Let C be the class or interface represented by this object:
NoSuchFieldException
is thrown. If this Class
object represents an array type, then this
method does not find the length
field of the array type.
name
- the field nameField
object of this class specified by
name
NoSuchFieldException
- if a field with the specified name is
not found.NullPointerException
- if name
is null
SecurityException
- If a security manager, s, is present and
the caller's class loader is not the same as or an
ancestor of the class loader for the current class and
invocation of s.checkPackageAccess()
denies access to the package
of this class.public Method getMethod(String name, Class<?>... parameterTypes) throws NoSuchMethodException, SecurityException
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 or interface represented by this object:
Object
, then this algorithm is
invoked recursively on the superclass of C.Object
, or if C is an interface, then
the superinterfaces of C (if any) are searched for a matching
method. If any such method is found, it is reflected.To find a matching method in a class or interface 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 with bridge methods; the bridge method and the method being overridden would have the same signature but different return types.
If this Class
object represents an array type, then this
method does not find the clone()
method.
Static methods declared in superinterfaces of the class or interface
represented by this Class
object are not considered members of
the class or interface.
name
- the name of the methodparameterTypes
- the list of parametersMethod
object that matches the specified
name
and parameterTypes
NoSuchMethodException
- if a matching method is not found
or if the name is "<init>"or "<clinit>".NullPointerException
- if name
is null
SecurityException
- If a security manager, s, is present and
the caller's class loader is not the same as or an
ancestor of the class loader for the current class and
invocation of s.checkPackageAccess()
denies access to the package
of this class.public Constructor<T> getConstructor(Class<?>... parameterTypes) throws NoSuchMethodException, SecurityException
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
.
parameterTypes
- the parameter arrayConstructor
object of the public constructor that
matches the specified parameterTypes
NoSuchMethodException
- if a matching method is not found.SecurityException
- If a security manager, s, is present and
the caller's class loader is not the same as or an
ancestor of the class loader for the current class and
invocation of s.checkPackageAccess()
denies access to the package
of this class.public Class<?>[] getDeclaredClasses() throws SecurityException
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.Class
objects representing all the
declared members of this classSecurityException
- If a security manager, s, is present and any of the
following conditions is met:
s.checkPermission
method with
RuntimePermission("accessDeclaredMembers")
denies access to the declared classes within this class
s.checkPackageAccess()
denies access to the package
of this class
public Field[] getDeclaredFields() throws SecurityException
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.
If this Class
object represents a class or interface with no
declared fields, then this method returns an array of length 0.
If this Class
object represents an array type, a primitive
type, or void, then this method returns an array of length 0.
The elements in the returned array are not sorted and are not in any particular order.
Field
objects representing all the
declared fields of this classSecurityException
- If a security manager, s, is present and any of the
following conditions is met:
s.checkPermission
method with
RuntimePermission("accessDeclaredMembers")
denies access to the declared fields within this class
s.checkPackageAccess()
denies access to the package
of this class
public Method[] getDeclaredMethods() throws SecurityException
Method
objects reflecting all the
declared methods of the class or interface represented by this Class
object, including public, protected, default (package)
access, and private methods, but excluding inherited methods.
If this Class
object represents a type that has multiple
declared methods with the same name and parameter types, but different
return types, then the returned array has a Method
object for
each such method.
If this Class
object represents a type that has a class
initialization method <clinit>
, then the returned array does
not have a corresponding Method
object.
If this Class
object represents a class or interface with no
declared methods, then the returned array has length 0.
If this Class
object represents an array type, a primitive
type, or void, then the returned array has length 0.
The elements in the returned array are not sorted and are not in any particular order.
Method
objects representing all the
declared methods of this classSecurityException
- If a security manager, s, is present and any of the
following conditions is met:
s.checkPermission
method with
RuntimePermission("accessDeclaredMembers")
denies access to the declared methods within this class
s.checkPackageAccess()
denies access to the package
of this class
public Constructor<?>[] getDeclaredConstructors() throws SecurityException
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. If the
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
void.
See The Java Language Specification, section 8.2.
Constructor
objects representing all the
declared constructors of this classSecurityException
- If a security manager, s, is present and any of the
following conditions is met:
s.checkPermission
method with
RuntimePermission("accessDeclaredMembers")
denies access to the declared constructors within this class
s.checkPackageAccess()
denies access to the package
of this class
public Field getDeclaredField(String name) throws NoSuchFieldException, SecurityException
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.
If this Class
object represents an array type, then this
method does not find the length
field of the array type.
name
- the name of the fieldField
object for the specified field in this
classNoSuchFieldException
- if a field with the specified name is
not found.NullPointerException
- if name
is null
SecurityException
- If a security manager, s, is present and any of the
following conditions is met:
s.checkPermission
method with
RuntimePermission("accessDeclaredMembers")
denies access to the declared field
s.checkPackageAccess()
denies access to the package
of this class
public Method getDeclaredMethod(String name, Class<?>... parameterTypes) throws NoSuchMethodException, SecurityException
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
returned; otherwise one of the methods is chosen arbitrarily. If the
name is "<init>"or "<clinit>" a NoSuchMethodException
is raised.
If this Class
object represents an array type, then this
method does not find the clone()
method.
name
- the name of the methodparameterTypes
- the parameter arrayMethod
object for the method of this class
matching the specified name and parametersNoSuchMethodException
- if a matching method is not found.NullPointerException
- if name
is null
SecurityException
- If a security manager, s, is present and any of the
following conditions is met:
s.checkPermission
method with
RuntimePermission("accessDeclaredMembers")
denies access to the declared method
s.checkPackageAccess()
denies access to the package
of this class
public Constructor<T> getDeclaredConstructor(Class<?>... parameterTypes) throws NoSuchMethodException, SecurityException
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.parameterTypes
- the parameter arrayConstructor
object for the constructor with the
specified parameter listNoSuchMethodException
- if a matching method is not found.SecurityException
- If a security manager, s, is present and any of the
following conditions is met:
s.checkPermission
method with
RuntimePermission("accessDeclaredMembers")
denies access to the declared constructor
s.checkPackageAccess()
denies access to the package
of this class
public InputStream getResourceAsStream(String name)
ClassLoader.getSystemResourceAsStream(java.lang.String)
.
Before delegation, an absolute resource name is constructed from the given resource name using this algorithm:
name
begins with a '/'
('\u002f'), then the absolute name of the resource is the
portion of the name
following the '/'
.
modified_package_name/name
Where the modified_package_name
is the package name of this
object with '/'
substituted for '.'
('\u002e').
name
- name of the desired resourceInputStream
object or null
if
no resource with this name is foundNullPointerException
- If name
is null
public URL getResource(String name)
ClassLoader.getSystemResource(java.lang.String)
.
Before delegation, an absolute resource name is constructed from the given resource name using this algorithm:
name
begins with a '/'
('\u002f'), then the absolute name of the resource is the
portion of the name
following the '/'
.
modified_package_name/name
Where the modified_package_name
is the package name of this
object with '/'
substituted for '.'
('\u002e').
name
- name of the desired resourceURL
object or null
if no
resource with this name is foundpublic ProtectionDomain getProtectionDomain()
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
.SecurityException
- if a security manager exists and its
checkPermission
method doesn't allow
getting the ProtectionDomain.ProtectionDomain
,
SecurityManager.checkPermission(java.security.Permission)
,
RuntimePermission
public boolean isAnnotation()
public boolean isSynthetic()
public Type getGenericSuperclass()
public Type[] getGenericInterfaces()
public Method getEnclosingMethod() throws SecurityException
Class
object represents a local or anonymous
class within a method, returns a Method
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.null
.SecurityException
- If a security manager, s, is present and any of the
following conditions is met:
s.checkPermission
method with
RuntimePermission("accessDeclaredMembers")
denies access to the methods within the enclosing class
s.checkPackageAccess()
denies access to the package
of the enclosing class
public Constructor<?> getEnclosingConstructor() throws SecurityException
Class
object represents a local or anonymous
class within a constructor, returns a Constructor
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.null
.SecurityException
- If a security manager, s, is present and any of the
following conditions is met:
s.checkPermission
method with
RuntimePermission("accessDeclaredMembers")
denies access to the constructors within the enclosing class
s.checkPackageAccess()
denies access to the package
of the enclosing class
public Class<?> getEnclosingClass() throws SecurityException
null
.SecurityException
- If a security manager, s, is present and the caller's
class loader is not the same as or an ancestor of the class
loader for the enclosing class and invocation of s.checkPackageAccess()
denies access to the package of the enclosing classpublic String getSimpleName()
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 "[]".
public String getTypeName()
getTypeName
in interface Type
public String getCanonicalName()
null
otherwise.public boolean isAnonymousClass()
true
if and only if the underlying class
is an anonymous class.true
if and only if this class is an anonymous class.public boolean isLocalClass()
true
if and only if the underlying class
is a local class.true
if and only if this class is a local class.public boolean isMemberClass()
true
if and only if the underlying class
is a member class.true
if and only if this class is a member class.public boolean desiredAssertionStatus()
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.
ClassLoader.setClassAssertionStatus(java.lang.String, boolean)
,
ClassLoader.setPackageAssertionStatus(java.lang.String, boolean)
,
ClassLoader.setDefaultAssertionStatus(boolean)
public boolean isEnum()
public T[] getEnumConstants()
public T cast(Object obj)
obj
- the object to be casted.ClassCastException
- if !isInstance(obj).public <U> Class<? extends U> asSubclass(Class<U> clazz)
clazz
- a subclass of thisClassCastException
- if this is not a subclass of clazz.public boolean isAnnotationPresent(Class<? extends Annotation> annotationClass)
AnnotatedElement
The truth value returned by this method is equivalent to:
getAnnotation(annotationClass) != null
The body of the default method is specified to be the code above.
isAnnotationPresent
in interface AnnotatedElement
annotationClass
- the Class object corresponding to the
annotation typeNullPointerException
- if the given annotation class is nullpublic <A extends Annotation> A[] getAnnotationsByType(Class<A> annotationClass)
AnnotatedElement
AnnotatedElement.getAnnotation(Class)
is that this method detects if its argument is a repeatable
annotation type (JLS 9.6), and if so, attempts to find one or
more annotations of that type by "looking through" a container
annotation.
The caller of this method is free to modify the returned array; it will
have no effect on the arrays returned to other callers.getAnnotationsByType
in interface AnnotatedElement
A
- the type of the annotation to query for and return if presentannotationClass
- the Class object corresponding to the
annotation typeNullPointerException
- if the given annotation class is nullpublic <A extends Annotation> A getAnnotation(Class<A> annotationClass)
AnnotatedElement
getAnnotation
in interface AnnotatedElement
A
- the type of the annotation to query for and return if presentannotationClass
- the Class object corresponding to the
annotation typeNullPointerException
- if the given annotation class is nullpublic Annotation[] getAnnotations()
AnnotatedElement
getAnnotations
in interface AnnotatedElement
public <A extends Annotation> A getDeclaredAnnotation(Class<A> annotationClass)
AnnotatedElement
getDeclaredAnnotation
in interface AnnotatedElement
A
- the type of the annotation to query for and return if directly presentannotationClass
- the Class object corresponding to the
annotation typeNullPointerException
- if the given annotation class is nullpublic <A extends Annotation> A[] getDeclaredAnnotationsByType(Class<A> annotationClass)
AnnotatedElement
AnnotatedElement.getDeclaredAnnotation(Class)
is that this method detects if its
argument is a repeatable annotation type (JLS 9.6), and if so,
attempts to find one or more annotations of that type by "looking
through" a container annotation if one is present.
The caller of this method is free to modify the returned array; it will
have no effect on the arrays returned to other callers.getDeclaredAnnotationsByType
in interface AnnotatedElement
A
- the type of the annotation to query for and return
if directly or indirectly presentannotationClass
- the Class object corresponding to the
annotation typeNullPointerException
- if the given annotation class is nullpublic Annotation[] getDeclaredAnnotations()
AnnotatedElement
getDeclaredAnnotations
in interface AnnotatedElement
public TypeVariable<Class<T>>[] getTypeParameters()
getTypeParameters
in interface GenericDeclaration
public AnnotatedType getAnnotatedSuperclass()
AnnotatedType
object that represents the use of a
type to specify the superclass of the entity represented by this Class
object. (The use of type Foo to specify the superclass
in '... extends Foo' is distinct from the declaration of type
Foo.)
If this Class
object represents a type whose declaration
does not explicitly indicate an annotated superclass, then the return
value is an AnnotatedType
object representing an element with no
annotations.
If this Class
represents either the Object
class, an
interface type, an array type, a primitive type, or void, the return
value is null
.
public AnnotatedType[] getAnnotatedInterfaces()
AnnotatedType
objects that represent the use
of types to specify superinterfaces of the entity represented by this
Class
object. (The use of type Foo to specify a
superinterface in '... implements Foo' is distinct from the
declaration of type Foo.)
If this Class
object represents a class, the return value is
an array containing objects representing the uses of interface types to
specify interfaces implemented by the class. The order of the objects in
the array corresponds to the order of the interface types used in the
'implements' clause of the declaration of this Class
object.
If this Class
object represents an interface, the return
value is an array containing objects representing the uses of interface
types to specify interfaces directly extended by the interface. The
order of the objects in the array corresponds to the order of the
interface types used in the 'extends' clause of the declaration of this
Class
object.
If this Class
object represents a class or interface whose
declaration does not explicitly indicate any annotated superinterfaces,
the return value is an array of length 0.
If this Class
object represents either the Object
class, an array type, a primitive type, or void, the return value is an
array of length 0.