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public
final
class
Class
extends Object
implements
Serializable,
GenericDeclaration,
Type,
AnnotatedElement
java.lang.Object | |
↳ | java.lang.Class<T> |
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
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());
Public methods | |
---|---|
<U>
Class<? extends U>
|
asSubclass(Class<U> clazz)
Casts this |
T
|
cast(Object obj)
Casts an object to the class or interface represented
by this |
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 name, boolean initialize, ClassLoader loader)
Returns the |
static
Class<?>
|
forName(String className)
Returns the |
<A extends Annotation>
A
|
getAnnotation(Class<A> annotationClass)
|
Annotation[]
|
getAnnotations()
Returns annotations that are present on this element. |
<A extends Annotation>
A[]
|
getAnnotationsByType(Class<A> annotationClass)
|
String
|
getCanonicalName()
Returns the canonical name of the underlying class as defined by the Java Language Specification. |
ClassLoader
|
getClassLoader()
Returns the class loader for the class. |
Class[]<?>
|
getClasses()
Returns an array containing |
Class<?>
|
getComponentType()
Returns the |
Constructor<T>
|
getConstructor(Class...<?> parameterTypes)
Returns a |
Constructor[]<?>
|
getConstructors()
Returns an array containing |
<A extends Annotation>
A
|
getDeclaredAnnotation(Class<A> annotationClass)
|
Annotation[]
|
getDeclaredAnnotations()
Returns annotations that are directly present on this element. |
Class[]<?>
|
getDeclaredClasses()
Returns an array of |
Constructor<T>
|
getDeclaredConstructor(Class...<?> parameterTypes)
Returns a |
Constructor[]<?>
|
getDeclaredConstructors()
Returns an array of |
Field
|
getDeclaredField(String name)
Returns a |
Field[]
|
getDeclaredFields()
Returns an array of |
Method
|
getDeclaredMethod(String name, Class...<?> parameterTypes)
Returns a |
Method[]
|
getDeclaredMethods()
Returns an array containing |
Class<?>
|
getDeclaringClass()
If the class or interface represented by this |
Class<?>
|
getEnclosingClass()
Returns the immediately enclosing class of the underlying class. |
Constructor<?>
|
getEnclosingConstructor()
If this |
Method
|
getEnclosingMethod()
If this |
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[]
|
getFields()
Returns an array containing |
Type[]
|
getGenericInterfaces()
Returns the |
Type
|
getGenericSuperclass()
Returns the |
Class[]<?>
|
getInterfaces()
Determines the interfaces implemented by the class or interface represented by this object. |
Method
|
getMethod(String name, Class...<?> parameterTypes)
Returns a |
Method[]
|
getMethods()
Returns an array containing |
int
|
getModifiers()
Returns the Java language modifiers for this class or interface, encoded in an integer. |
String
|
getName()
Returns the name of the entity (class, interface, array class,
primitive type, or void) represented by this |
Package
|
getPackage()
Gets the package for this class. |
String
|
getPackageName()
Returns the fully qualified package name. |
ProtectionDomain
|
getProtectionDomain()
Returns the |
URL
|
getResource(String name)
Finds a resource with a given name. |
InputStream
|
getResourceAsStream(String name)
Finds a resource with a given name. |
Object[]
|
getSigners()
Gets the signers of this class. |
String
|
getSimpleName()
Returns the simple name of the underlying class as given in the source code. |
Class<? super T>
|
getSuperclass()
Returns the |
String
|
getTypeName()
Return an informative string for the name of this type. |
TypeVariable[]<Class<T>>
|
getTypeParameters()
Returns an array of |
boolean
|
isAnnotation()
Returns true if this |
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 |
boolean
|
isArray()
Determines if this |
boolean
|
isAssignableFrom(Class<?> cls)
Determines if the class or interface represented by this
|
boolean
|
isEnum()
Returns true if and only if this class was declared as an enum in the source code. |
boolean
|
isInstance(Object obj)
Determines if the specified |
boolean
|
isInterface()
Determines if the specified |
boolean
|
isLocalClass()
Returns |
boolean
|
isMemberClass()
Returns |
boolean
|
isPrimitive()
Determines if the specified |
boolean
|
isSynthetic()
Returns |
T
|
newInstance()
Creates a new instance of the class represented by this |
String
|
toGenericString()
Returns a string describing this |
String
|
toString()
Converts the object to a string. |
Inherited methods | |
---|---|
public Class<? extends U> asSubclass (Class<U> clazz)
Casts this Class
object to represent a subclass of the class
represented by the specified class object. Checks that the cast
is valid, and throws a ClassCastException
if it is not. If
this method succeeds, it always returns a reference to this class object.
This method is useful when a client needs to "narrow" the type of
a Class
object to pass it to an API that restricts 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).
Parameters | |
---|---|
clazz |
Class : the class of the type to cast this class object to |
Returns | |
---|---|
Class<? extends U> |
this Class object, cast to represent a subclass of
the specified class object. |
Throws | |
---|---|
ClassCastException |
if this Class object does not
represent a subclass of the specified class (here "subclass" includes
the class itself). |
public T cast (Object obj)
Casts an object to the class or interface represented
by this Class
object.
Parameters | |
---|---|
obj |
Object : the object to be cast |
Returns | |
---|---|
T |
the object after casting, or null if obj is null |
Throws | |
---|---|
ClassCastException |
if the object is not null and is not assignable to the type T. |
public boolean desiredAssertionStatus ()
Returns the assertion status that would be assigned to this class if it were to be initialized at the time this method is invoked. If this class has had its assertion status set, the most recent setting will be returned; otherwise, if any package default assertion status pertains to this class, the most recent setting for the most specific pertinent package default assertion status is returned; otherwise, if this class is not a system class (i.e., it has a class loader) its class loader's default assertion status is returned; otherwise, the system class default assertion status is returned.
Few programmers will have any need for this method; it is provided for the benefit of the JRE itself. (It allows a class to determine at the time that it is initialized whether assertions should be enabled.) Note that this method is not guaranteed to return the actual assertion status that was (or will be) associated with the specified class when it was (or will be) initialized.
Returns | |
---|---|
boolean |
the desired assertion status of the specified class. |
public 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.
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 |
String : fully qualified name of the desired class |
initialize |
boolean : if true the class will be initialized.
See Section 12.4 of The Java Language Specification. |
loader |
ClassLoader : class loader from which the class must be loaded |
Returns | |
---|---|
Class<?> |
class object representing the desired class |
Throws | |
---|---|
LinkageError |
if the linkage fails |
ExceptionInInitializerError |
if the initialization provoked by this method fails |
ClassNotFoundException |
if the class cannot be located by the specified class loader |
See also:
public static Class<?> forName (String 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 |
String : the fully qualified name of the desired class. |
Returns | |
---|---|
Class<?> |
the Class object for the class with the
specified name. |
Throws | |
---|---|
LinkageError |
if the linkage fails |
ExceptionInInitializerError |
if the initialization provoked by this method fails |
ClassNotFoundException |
if the class cannot be located |
public A getAnnotation (Class<A> annotationClass)
Parameters | |
---|---|
annotationClass |
Class |
Returns | |
---|---|
A |
Throws | |
---|---|
NullPointerException |
public Annotation[] getAnnotations ()
Returns annotations that are present on this element. If there are no annotations present on this element, the return value is an array of length 0. The caller of this method is free to modify the returned array; it will have no effect on the arrays returned to other callers.
Returns | |
---|---|
Annotation[] |
annotations present on this element |
public A[] getAnnotationsByType (Class<A> annotationClass)
Parameters | |
---|---|
annotationClass |
Class |
Returns | |
---|---|
A[] |
Throws | |
---|---|
NullPointerException |
public String getCanonicalName ()
Returns the canonical name of the underlying class as defined by the Java Language Specification. Returns null if the underlying class does not have a canonical name (i.e., if it is a local or anonymous class or an array whose component type does not have a canonical name).
Returns | |
---|---|
String |
the canonical name of the underlying class if it exists, and
null otherwise. |
public ClassLoader getClassLoader ()
Returns the class loader for the class. Some implementations may use null to represent the bootstrap class loader. This method will return null in such implementations if this class was loaded by the bootstrap class loader.
If a security manager is present, and the caller's class loader is
not null and the caller's class loader is not the same as or an ancestor of
the class loader for the class whose class loader is requested, then
this method calls the security manager's checkPermission
method with 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 | |
---|---|
ClassLoader |
the class loader that loaded the class or interface represented by this object. |
Throws | |
---|---|
SecurityException |
if a security manager exists and its
checkPermission method denies
access to the class loader for the class. |
public 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. 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 | |
---|---|
Class[]<?> |
the array of Class objects representing the public
members of this class |
public Class<?> getComponentType ()
Returns the Class
representing the component type of an
array. If this class does not represent an array class this method
returns null.
Returns | |
---|---|
Class<?> |
the Class representing the component type of this
class if this class is an array |
See also:
public Constructor<T> getConstructor (Class...<?> 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 |
Class : the parameter array |
Returns | |
---|---|
Constructor<T> |
the Constructor object of the public constructor that
matches the specified parameterTypes |
Throws | |
---|---|
NoSuchMethodException |
if a matching method is not found. |
SecurityException |
If a security manager, s, is present and
the caller's class loader is not the same as or an
ancestor of the class loader for the current class and
invocation of s.checkPackageAccess() denies access to the package
of this class. |
public Constructor[]<?> 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 | |
---|---|
Constructor[]<?> |
the array of Constructor objects representing the
public constructors of this class |
Throws | |
---|---|
SecurityException |
If a security manager, s, is present and
the caller's class loader is not the same as or an
ancestor of the class loader for the current class and
invocation of s.checkPackageAccess() denies access to the package
of this class. |
public A getDeclaredAnnotation (Class<A> annotationClass)
Parameters | |
---|---|
annotationClass |
Class |
Returns | |
---|---|
A |
Throws | |
---|---|
NullPointerException |
public Annotation[] getDeclaredAnnotations ()
Returns annotations that are directly present on this element. This method ignores inherited annotations. If there are no annotations directly present on this element, the return value is an array of length 0. The caller of this method is free to modify the returned array; it will have no effect on the arrays returned to other callers.
Returns | |
---|---|
Annotation[] |
annotations directly present on this element |
public 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. 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 | |
---|---|
Class[]<?> |
the array of Class objects representing all the
declared members of this class |
Throws | |
---|---|
SecurityException |
If a security manager, s, is present and any of the
following conditions is met:
|
public Constructor<T> getDeclaredConstructor (Class...<?> 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 |
Class : the parameter array |
Returns | |
---|---|
Constructor<T> |
The Constructor object for the constructor with the
specified parameter list |
Throws | |
---|---|
NoSuchMethodException |
if a matching method is not found. |
SecurityException |
If a security manager, s, is present and any of the
following conditions is met:
|
public Constructor[]<?> 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. 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.
Returns | |
---|---|
Constructor[]<?> |
the array of Constructor objects representing all the
declared constructors of this class |
Throws | |
---|---|
SecurityException |
If a security manager, s, is present and any of the
following conditions is met:
|
public Field getDeclaredField (String 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.
If this Class
object represents an array type, then this
method does not find the length
field of the array type.
Parameters | |
---|---|
name |
String : the name of the field |
Returns | |
---|---|
Field |
the Field object for the specified field in this
class |
Throws | |
---|---|
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 any of the
following conditions is met:
|
public Field[] 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.
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.
Returns | |
---|---|
Field[] |
the array of Field objects representing all the
declared fields of this class |
Throws | |
---|---|
SecurityException |
If a security manager, s, is present and any of the
following conditions is met:
|
public 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. 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.
Parameters | |
---|---|
name |
String : the name of the method |
parameterTypes |
Class : the parameter array |
Returns | |
---|---|
Method |
the Method object for the method of this class
matching the specified name and parameters |
Throws | |
---|---|
NoSuchMethodException |
if a matching method is not found. |
NullPointerException |
if name is null |
SecurityException |
If a security manager, s, is present and any of the
following conditions is met:
|
public 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.
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.
Returns | |
---|---|
Method[] |
the array of Method objects representing all the
declared methods of this class |
Throws | |
---|---|
SecurityException |
If a security manager, s, is present and any of the
following conditions is met:
|
public 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. 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.
Returns | |
---|---|
Class<?> |
the declaring class for this class |
public Class<?> getEnclosingClass ()
Returns the immediately enclosing class of the underlying
class. If the underlying class is a top level class this
method returns null
.
Returns | |
---|---|
Class<?> |
the immediately enclosing class of the underlying class |
public 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. 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 | |
---|---|
Constructor<?> |
the immediately enclosing constructor of the underlying class, if
that class is a local or anonymous class; otherwise null . |
public 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. 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 | |
---|---|
Method |
the immediately enclosing method of the underlying class, if
that class is a local or anonymous class; otherwise null . |
public T[] getEnumConstants ()
Returns the elements of this enum class or null if this Class object does not represent an enum type.
Returns | |
---|---|
T[] |
an array containing the values comprising the enum class represented by this Class object in the order they're declared, or null if this Class object does not represent an enum type |
public 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. 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.
Parameters | |
---|---|
name |
String : the field name |
Returns | |
---|---|
Field |
the Field object of this class specified by
name |
Throws | |
---|---|
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 Field[] getFields ()
Returns an array containing 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.
Returns | |
---|---|
Field[] |
the array of Field objects representing the
public fields |
Throws | |
---|---|
SecurityException |
If a security manager, s, is present and
the caller's class loader is not the same as or an
ancestor of the class loader for the current class and
invocation of s.checkPackageAccess() denies access to the package
of this class. |
public Type[] getGenericInterfaces ()
Returns the Type
s representing the interfaces
directly implemented by the class or interface represented by
this object.
If a superinterface is a parameterized type, the
Type
object returned for it must accurately reflect
the actual type parameters used in the source code. The
parameterized type representing each superinterface is created
if it had not been created before. See the declaration of
ParameterizedType
for the semantics of the creation process for parameterized
types.
If this object represents a class, the return value is an
array containing objects representing all interfaces
implemented by the class. The order of the interface objects in
the array corresponds to the order of the interface names in
the implements
clause of the declaration of the class
represented by this object. In the case of an array class, the
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 0.
If this object represents a primitive type or void, the method returns an array of length 0.
Returns | |
---|---|
Type[] |
an array of interfaces implemented by this class |
Throws | |
---|---|
GenericSignatureFormatError |
if the generic class signature does not conform to the format specified in The Java™ Virtual Machine Specification |
TypeNotPresentException |
if any of the generic superinterfaces refers to a non-existent type declaration |
MalformedParameterizedTypeException |
if any of the generic superinterfaces refer to a parameterized type that cannot be instantiated for any reason |
public Type 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 ParameterizedType
for the
semantics of the creation process for parameterized types. 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
returned.
Returns | |
---|---|
Type |
the superclass of the class represented by this object |
Throws | |
---|---|
GenericSignatureFormatError |
if the generic class signature does not conform to the format specified in The Java™ Virtual Machine Specification |
TypeNotPresentException |
if the generic superclass refers to a non-existent type declaration |
MalformedParameterizedTypeException |
if the generic superclass refers to a parameterized type that cannot be instantiated for any reason |
public Class[]<?> getInterfaces ()
Determines the interfaces implemented by the class or interface represented by this object.
If this object represents a class, the return value is an array
containing objects representing all interfaces implemented by the
class. The order of the interface objects in the array corresponds to
the order of the interface names in the implements
clause
of the declaration of the class represented by this object. For
example, given the declaration:
class Shimmer implements FloorWax, DessertTopping { ... }
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.
If this Class
object represents an array type, the
interfaces Cloneable
and java.io.Serializable
are
returned in that order.
Returns | |
---|---|
Class[]<?> |
an array of interfaces implemented by this class. |
public 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. 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.
Parameters | |
---|---|
name |
String : the name of the method |
parameterTypes |
Class : the list of parameters |
Returns | |
---|---|
Method |
the Method object that matches the specified
name and parameterTypes |
Throws | |
---|---|
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 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.
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.
Returns | |
---|---|
Method[] |
the array of Method objects representing the
public methods of this class |
Throws | |
---|---|
SecurityException |
If a security manager, s, is present and
the caller's class loader is not the same as or an
ancestor of the class loader for the current class and
invocation of s.checkPackageAccess() denies access to the package
of this class. |
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. If this
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 | |
---|---|
int |
the int representing the modifiers for this class |
See also:
public String 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 by The Java™ Language Specification.
If this class object represents a primitive type or void, then the
name returned is a String
equal to the Java language
keyword corresponding to the primitive type or void.
If this class object represents a class of arrays, then the internal
form of the name consists of the name of the element type preceded by
one or more '[
' characters representing the depth of the array
nesting. The encoding of element type names is as follows:
Element Type Encoding boolean Z byte B char C class or interface Lclassname; double D float F int I long J short S
The class or interface name classname is the binary name of the class specified above.
Examples:
String.class.getName() returns "java.lang.String" byte.class.getName() returns "byte" (new Object[3]).getClass().getName() returns "[Ljava.lang.Object;" (new int[3][4][5][6][7][8][9]).getClass().getName() returns "[[[[[[[I"
Returns | |
---|---|
String |
the name of the class or interface represented by this object. |
public Package getPackage ()
Gets the package for this class. The class loader of this class is used to find the package. If the class was loaded by the bootstrap class loader the set of packages loaded from CLASSPATH is searched to find the package of the class. Null is returned if no package object was created by the class loader of this class.
Packages have attributes for versions and specifications only if the information was defined in the manifests that accompany the classes, and if the class loader created the package instance with the attributes from the manifest.
Returns | |
---|---|
Package |
the package of the class, or null if no package information is available from the archive or codebase. |
public String getPackageName ()
Returns the fully qualified package name.
If this class is a top level class, then this method returns the fully qualified name of the package that the class is a member of, or the empty string if the class is in an unnamed package.
If this class is a member class, then this method is equivalent to
invoking getPackageName()
on the enclosing class.
If this class is a local class or an anonymous class, then this method is equivalent to
invoking getPackageName()
on the declaring class of the enclosing method or
enclosing constructor.
If this class represents an array type then this method returns the
package name of the element type. If this class represents a primitive
type or void then the package name "java.lang
" is returned.
Returns | |
---|---|
String |
the fully qualified package name |
public ProtectionDomain 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 | |
---|---|
ProtectionDomain |
the ProtectionDomain of this class |
Throws | |
---|---|
SecurityException |
if a security manager exists and its
checkPermission method doesn't allow
getting the ProtectionDomain. |
public URL getResource (String name)
Finds a resource with a given name. The rules for searching resources
associated with a given class are implemented by the defining
class loader of the class. This method
delegates to this object's class loader. If this object was loaded by
the bootstrap class loader, the method delegates to ClassLoader.getSystemResource(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').
Parameters | |
---|---|
name |
String : name of the desired resource |
Returns | |
---|---|
URL |
A URL object or null if no
resource with this name is found |
public InputStream getResourceAsStream (String name)
Finds a resource with a given name. The rules for searching resources
associated with a given class are implemented by the defining
class loader of the class. This method
delegates to this object's class loader. If this object was loaded by
the bootstrap class loader, the method delegates to ClassLoader.getSystemResourceAsStream(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').
Parameters | |
---|---|
name |
String : name of the desired resource |
Returns | |
---|---|
InputStream |
A InputStream object or null if
no resource with this name is found |
Throws | |
---|---|
NullPointerException |
If name is null |
public Object[] getSigners ()
Gets the signers of this class.
Returns | |
---|---|
Object[] |
the signers of this class, or null if there are no signers. In particular, this method returns null if this object represents a primitive type or void. |
public String getSimpleName ()
Returns the simple name of the underlying class as given in the source code. Returns an empty string if the underlying class is anonymous.
The simple name of an array is the simple name of the component type with "[]" appended. In particular the simple name of an array whose component type is anonymous is "[]".
Returns | |
---|---|
String |
the simple name of the underlying class |
public Class<? super T> getSuperclass ()
Returns the Class
representing the superclass of the entity
(class, interface, primitive type or void) represented by this
Class
. 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
returned.
Returns | |
---|---|
Class<? super T> |
the superclass of the class represented by this object. |
public String getTypeName ()
Return an informative string for the name of this type.
Returns | |
---|---|
String |
an informative string for the name of this type |
public TypeVariable[]<Class<T>> 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.
Returns | |
---|---|
TypeVariable[]<Class<T>> |
an array of TypeVariable objects that represent
the type variables declared by this generic declaration |
Throws | |
---|---|
GenericSignatureFormatError |
if the generic signature of this generic declaration does not conform to the format specified in The Java™ Virtual Machine Specification |
public boolean isAnnotation ()
Returns true if this Class
object represents an annotation
type. Note that if this method returns true, isInterface()
would also return true, as all annotation types are also interfaces.
Returns | |
---|---|
boolean |
true if this class object represents an annotation
type; false otherwise |
public boolean isAnnotationPresent (Class<? extends Annotation> annotationClass)
Returns true if an annotation for the specified type is present on this element, else false. This method is designed primarily for convenient access to marker annotations.
The truth value returned by this method is equivalent to:
getAnnotation(annotationClass) != null
The body of the default method is specified to be the code above.
Parameters | |
---|---|
annotationClass |
Class : the Class object corresponding to the
annotation type |
Returns | |
---|---|
boolean |
true if an annotation for the specified annotation type is present on this element, else false |
Throws | |
---|---|
NullPointerException |
public boolean isAnonymousClass ()
Returns true
if and only if the underlying class
is an anonymous class.
Returns | |
---|---|
boolean |
true if and only if this class is an anonymous class. |
public boolean isArray ()
Determines if this Class
object represents an array class.
Returns | |
---|---|
boolean |
true if this object represents an array class;
false otherwise. |
public boolean isAssignableFrom (Class<?> 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
if so;
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
object; otherwise it returns
false
.
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 |
Class : the Class object to be checked |
Returns | |
---|---|
boolean |
the boolean value indicating whether objects of the
type cls can be assigned to objects of this class |
Throws | |
---|---|
NullPointerException |
if the specified Class parameter is null. |
public boolean isEnum ()
Returns true if and only if this class was declared as an enum in the source code.
Returns | |
---|---|
boolean |
true if and only if this class was declared as an enum in the source code |
public boolean isInstance (Object 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 reference conversion; 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
implements this interface; it returns false
otherwise. If
this Class
object represents a primitive type, this method
returns false
.
Parameters | |
---|---|
obj |
Object : the object to check |
Returns | |
---|---|
boolean |
true if obj is an instance of this class |
public boolean isInterface ()
Determines if the specified Class
object represents an
interface type.
Returns | |
---|---|
boolean |
true if this object represents an interface;
false otherwise. |
public boolean isLocalClass ()
Returns true
if and only if the underlying class
is a local class.
Returns | |
---|---|
boolean |
true if and only if this class is a local class. |
public boolean isMemberClass ()
Returns true
if and only if the underlying class
is a member class.
Returns | |
---|---|
boolean |
true if and only if this class is a member class. |
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 | |
---|---|
boolean |
true if and only if this class represents a primitive type |
public boolean isSynthetic ()
Returns true
if this class is a synthetic class;
returns false
otherwise.
Returns | |
---|---|
boolean |
true if and only if this class is a synthetic class as
defined by the Java Language Specification. |
public T newInstance ()
Creates a new instance of the class represented by this 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
.
Returns | |
---|---|
T |
a newly allocated instance of the class represented by this object. |
Throws | |
---|---|
IllegalAccessException |
if the class or its nullary constructor is not accessible. |
InstantiationException |
if 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 String toGenericString ()
Returns a string describing this 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.
Returns | |
---|---|
String |
a string describing this Class , including
information about modifiers and type parameters |
public String toString ()
Converts the object to a string. The string representation is the
string "class" or "interface", followed by a space, and then by the
fully qualified name of the class in the format returned by
getName
. If this Class
object represents a
primitive type, this method returns the name of the primitive type. If
this Class
object represents void this method returns
"void".
Returns | |
---|---|
String |
a string representation of this class object. |