java.lang
Class Class
- Serializable
A Class represents a Java type. There will never be multiple Class
objects with identical names and ClassLoaders. Primitive types, array
types, and void also have a Class object.
Arrays with identical type and number of dimensions share the same class.
The array class ClassLoader is the same as the ClassLoader of the element
type of the array (which can be null to indicate the bootstrap classloader).
The name of an array class is
[<signature format>;
.
For example,
String[]'s class is
[Ljava.lang.String;
. boolean, byte,
short, char, int, long, float and double have the "type name" of
Z,B,S,C,I,J,F,D for the purposes of array classes. If it's a
multidimensioned array, the same principle applies:
int[][][]
==
[[[I
.
There is no public constructor - Class objects are obtained only through
the virtual machine, as defined in ClassLoaders.
boolean | desiredAssertionStatus() - Returns the desired assertion status of this class, if it were to be
initialized at this moment.
|
static Class | forName(String name) - Use the classloader of the current class to load, link, and initialize
a class.
|
static Class | forName(String name, boolean initialize, ClassLoader classloader) - Use the specified classloader to load and link a class.
|
ClassLoader | getClassLoader() - Get the ClassLoader that loaded this class.
|
Class[] | getClasses() - Get all the public member classes and interfaces declared in this
class or inherited from superclasses.
|
Class | getComponentType() - If this is an array, get the Class representing the type of array.
|
Constructor | getConstructor(Class[] types) - Get a public constructor declared in this class.
|
Constructor[] | getConstructors() - Get all the public constructors of this class.
|
Class[] | getDeclaredClasses() - Get all the declared member classes and interfaces in this class, but
not those inherited from superclasses.
|
Constructor | getDeclaredConstructor(Class[] types) - Get a constructor declared in this class.
|
Constructor[] | getDeclaredConstructors() - Get all the declared constructors of this class.
|
Field | getDeclaredField(String name) - Get a field declared in this class, where name is its simple name.
|
Field[] | getDeclaredFields() - Get all the declared fields in this class, but not those inherited from
superclasses.
|
Method | getDeclaredMethod(String methodName, Class[] types) - Get a method declared in this class, where name is its simple name.
|
Method[] | getDeclaredMethods() - Get all the declared methods in this class, but not those inherited from
superclasses.
|
Class | getDeclaringClass() - If this is a nested or inner class, return the class that declared it.
|
Field | getField(String fieldName) - Get a public field declared or inherited in this class, where name is
its simple name.
|
Field[] | getFields() - Get all the public fields declared in this class or inherited from
superclasses.
|
Class[] | getInterfaces() - Get the interfaces this class directly implements, in the
order that they were declared.
|
Method | getMethod(String methodName, Class[] types) - Get a public method declared or inherited in this class, where name is
its simple name.
|
Method[] | getMethods() - Get all the public methods declared in this class or inherited from
superclasses.
|
int | getModifiers() - Get the modifiers of this class.
|
String | getName() - Get the name of this class, separated by dots for package separators.
|
Package | getPackage() - Returns the
Package in which this class is defined
Returns null when this information is not available from the
classloader of this class.
|
ProtectionDomain | getProtectionDomain() - Returns the protection domain of this class.
|
URL | getResource(String resourceName) - Get a resource URL using this class's package using the
getClassLoader().getResource() method.
|
InputStream | getResourceAsStream(String resourceName) - Get a resource using this class's package using the
getClassLoader().getResourceAsStream() method.
|
Object[] | getSigners() - Get the signers of this class.
|
Class | getSuperclass() - Get the direct superclass of this class.
|
boolean | isArray() - Return whether this class is an array type.
|
boolean | isAssignableFrom(Class c) - Discover whether an instance of the Class parameter would be an
instance of this Class as well.
|
boolean | isInstance(Object o) - Discover whether an Object is an instance of this Class.
|
boolean | isInterface() - Check whether this class is an interface or not.
|
boolean | isPrimitive() - Return whether this class is a primitive type.
|
Object | newInstance() - Get a new instance of this class by calling the no-argument constructor.
|
String | toString() - Return the human-readable form of this Object.
|
clone , equals , finalize , getClass , hashCode , notify , notifyAll , toString , wait , wait , wait |
desiredAssertionStatus
public boolean desiredAssertionStatus()
Returns the desired assertion status of this class, if it were to be
initialized at this moment. The class assertion status, if set, is
returned; the backup is the default package status; then if there is
a class loader, that default is returned; and finally the system default
is returned. This method seldom needs calling in user code, but exists
for compilers to implement the assert statement. Note that there is no
guarantee that the result of this method matches the class's actual
assertion status.
- the desired assertion status
forName
public static Class forName(String name)
throws ClassNotFoundException
Use the classloader of the current class to load, link, and initialize
a class. This is equivalent to your code calling
Class.forName(name, true, getClass().getClassLoader())
.
name
- the name of the class to find
- the Class object representing the class
forName
public static Class forName(String name,
boolean initialize,
ClassLoader classloader)
throws ClassNotFoundException
Use the specified classloader to load and link a class. If the loader
is null, this uses the bootstrap class loader (provide the security
check succeeds). Unfortunately, this method cannot be used to obtain
the Class objects for primitive types or for void, you have to use
the fields in the appropriate java.lang wrapper classes.
Calls
classloader.loadclass(name, initialize)
.
name
- the name of the class to findinitialize
- whether or not to initialize the class at this timeclassloader
- the classloader to use to find the class; null means
to use the bootstrap class loader
- the class object for the given class
ClassNotFoundException
- if the class was not found by the
classloaderSecurityException
- if the classloader
argument
is null
and the caller does not have the
RuntimePermission("getClassLoader")
permission
getClassLoader
public ClassLoader getClassLoader()
Get the ClassLoader that loaded this class. If the class was loaded
by the bootstrap classloader, this method will return null.
If there is a security manager, and the caller's class loader is not
an ancestor of the requested one, a security check of
RuntimePermission("getClassLoader")
must first succeed. Primitive types and void return null.
- the ClassLoader that loaded this class
getClasses
public Class[] getClasses()
Get all the public member classes and interfaces declared in this
class or inherited from superclasses. This returns an array of length
0 if there are no member classes, including for primitive types. A
security check may be performed, with
checkMemberAccess(this, Member.PUBLIC)
as well as
checkPackageAccess
both having to succeed.
- all public member classes in this class
getComponentType
public Class getComponentType()
If this is an array, get the Class representing the type of array.
Examples: "[[Ljava.lang.String;" would return "[Ljava.lang.String;", and
calling getComponentType on that would give "java.lang.String". If
this is not an array, returns null.
- the array type of this class, or null
getConstructor
public Constructor getConstructor(Class[] types)
throws NoSuchMethodException
Get a public constructor declared in this class. If the constructor takes
no argument, an array of zero elements and null are equivalent for the
types argument. A security check may be performed, with
checkMemberAccess(this, Member.PUBLIC)
as well as
checkPackageAccess
both having to succeed.
types
- the type of each parameter
getConstructors
public Constructor[] getConstructors()
Get all the public constructors of this class. This returns an array of
length 0 if there are no constructors, including for primitive types,
arrays, and interfaces. It does, however, include the default
constructor if one was supplied by the compiler. A security check may
be performed, with checkMemberAccess(this, Member.PUBLIC)
as well as checkPackageAccess
both having to succeed.
- all public constructors in this class
getDeclaredClasses
public Class[] getDeclaredClasses()
Get all the declared member classes and interfaces in this class, but
not those inherited from superclasses. This returns an array of length
0 if there are no member classes, including for primitive types. A
security check may be performed, with
checkMemberAccess(this, Member.DECLARED)
as well as
checkPackageAccess
both having to succeed.
- all declared member classes in this class
getDeclaredConstructor
public Constructor getDeclaredConstructor(Class[] types)
throws NoSuchMethodException
Get a constructor declared in this class. If the constructor takes no
argument, an array of zero elements and null are equivalent for the
types argument. A security check may be performed, with
checkMemberAccess(this, Member.DECLARED)
as well as
checkPackageAccess
both having to succeed.
types
- the type of each parameter
getDeclaredConstructors
public Constructor[] getDeclaredConstructors()
Get all the declared constructors of this class. This returns an array of
length 0 if there are no constructors, including for primitive types,
arrays, and interfaces. It does, however, include the default
constructor if one was supplied by the compiler. A security check may
be performed, with checkMemberAccess(this, Member.DECLARED)
as well as checkPackageAccess
both having to succeed.
- all constructors in this class
getDeclaredField
public Field getDeclaredField(String name)
throws NoSuchFieldException
Get a field declared in this class, where name is its simple name. The
implicit length field of arrays is not available. A security check may
be performed, with checkMemberAccess(this, Member.DECLARED)
as well as checkPackageAccess
both having to succeed.
name
- the name of the field
getDeclaredFields
public Field[] getDeclaredFields()
Get all the declared fields in this class, but not those inherited from
superclasses. This returns an array of length 0 if there are no fields,
including for primitive types. This does not return the implicit length
field of arrays. A security check may be performed, with
checkMemberAccess(this, Member.DECLARED)
as well as
checkPackageAccess
both having to succeed.
- all declared fields in this class
getDeclaredMethod
public Method getDeclaredMethod(String methodName,
Class[] types)
throws NoSuchMethodException
Get a method declared in this class, where name is its simple name. The
implicit methods of Object are not available from arrays or interfaces.
Constructors (named "<init>" in the class file) and class initializers
(name "<clinit>") are not available. The Virtual Machine allows
multiple methods with the same signature but differing return types; in
such a case the most specific return types are favored, then the final
choice is arbitrary. If the method takes no argument, an array of zero
elements and null are equivalent for the types argument. A security
check may be performed, with
checkMemberAccess(this, Member.DECLARED)
as well as
checkPackageAccess
both having to succeed.
methodName
- the name of the methodtypes
- the type of each parameter
getDeclaredMethods
public Method[] getDeclaredMethods()
Get all the declared methods in this class, but not those inherited from
superclasses. This returns an array of length 0 if there are no methods,
including for primitive types. This does include the implicit methods of
arrays and interfaces which mirror methods of Object, nor does it
include constructors or the class initialization methods. The Virtual
Machine allows multiple methods with the same signature but differing
return types; all such methods are in the returned array. A security
check may be performed, with
checkMemberAccess(this, Member.DECLARED)
as well as
checkPackageAccess
both having to succeed.
- all declared methods in this class
getDeclaringClass
public Class getDeclaringClass()
If this is a nested or inner class, return the class that declared it.
If not, return null.
- the declaring class of this class
getField
public Field getField(String fieldName)
throws NoSuchFieldException
Get a public field declared or inherited in this class, where name is
its simple name. If the class contains multiple accessible fields by
that name, an arbitrary one is returned. The implicit length field of
arrays is not available. A security check may be performed, with
checkMemberAccess(this, Member.PUBLIC)
as well as
checkPackageAccess
both having to succeed.
fieldName
- the name of the field
getFields
public Field[] getFields()
Get all the public fields declared in this class or inherited from
superclasses. This returns an array of length 0 if there are no fields,
including for primitive types. This does not return the implicit length
field of arrays. A security check may be performed, with
checkMemberAccess(this, Member.PUBLIC)
as well as
checkPackageAccess
both having to succeed.
- all public fields in this class
getInterfaces
public Class[] getInterfaces()
Get the interfaces this class directly implements, in the
order that they were declared. This returns an empty array, not null,
for Object, primitives, void, and classes or interfaces with no direct
superinterface. Array types return Cloneable and Serializable.
- the interfaces this class directly implements
getMethod
public Method getMethod(String methodName,
Class[] types)
throws NoSuchMethodException
Get a public method declared or inherited in this class, where name is
its simple name. The implicit methods of Object are not available from
interfaces. Constructors (named "<init>" in the class file) and class
initializers (name "<clinit>") are not available. The Virtual
Machine allows multiple methods with the same signature but differing
return types, and the class can inherit multiple methods of the same
return type; in such a case the most specific return types are favored,
then the final choice is arbitrary. If the method takes no argument, an
array of zero elements and null are equivalent for the types argument.
A security check may be performed, with
checkMemberAccess(this, Member.PUBLIC)
as well as
checkPackageAccess
both having to succeed.
methodName
- the name of the methodtypes
- the type of each parameter
getMethods
public Method[] getMethods()
Get all the public methods declared in this class or inherited from
superclasses. This returns an array of length 0 if there are no methods,
including for primitive types. This does not include the implicit
methods of interfaces which mirror methods of Object, nor does it
include constructors or the class initialization methods. The Virtual
Machine allows multiple methods with the same signature but differing
return types; all such methods are in the returned array. A security
check may be performed, with
checkMemberAccess(this, Member.PUBLIC)
as well as
checkPackageAccess
both having to succeed.
- all public methods in this class
getModifiers
public int getModifiers()
Get the modifiers of this class. These can be decoded using Modifier,
and is limited to one of public, protected, or private, and any of
final, static, abstract, or interface. An array class has the same
public, protected, or private modifier as its component type, and is
marked final but not an interface. Primitive types and void are marked
public and final, but not an interface.
- the modifiers of this class
getName
public String getName()
Get the name of this class, separated by dots for package separators.
If the class represents a primitive type, or void, then the
name of the type as it appears in the Java programming language
is returned. For instance,
Byte.TYPE.getName()
returns "byte".
Arrays are specially encoded as shown on this table.
array type [element type
(note that the element type is encoded per
this table)
boolean Z
byte B
char C
short S
int I
long J
float F
double D
void V
class or interface, alone: <dotted name>
class or interface, as element type: L<dotted name>;
getPackage
public Package getPackage()
Returns the Package
in which this class is defined
Returns null when this information is not available from the
classloader of this class.
- the package for this class, if it is available
getProtectionDomain
public ProtectionDomain getProtectionDomain()
Returns the protection domain of this class. If the classloader did not
record the protection domain when creating this class the unknown
protection domain is returned which has a null
code source
and all permissions. A security check may be performed, with
RuntimePermission("getProtectionDomain")
.
SecurityException
- if the security manager exists and the caller
does not have RuntimePermission("getProtectionDomain")
.
getResource
public URL getResource(String resourceName)
Get a resource URL using this class's package using the
getClassLoader().getResource() method. If this class was loaded using
the system classloader, ClassLoader.getSystemResource() is used instead.
If the name you supply is absolute (it starts with a
/
),
then the leading
/
is removed and it is passed on to
getResource(). If it is relative, the package name is prepended, and
.
's are replaced with
/
.
The URL returned is system- and classloader-dependent, and could
change across implementations.
resourceName
- the name of the resource, generally a path
getResourceAsStream
public InputStream getResourceAsStream(String resourceName)
Get a resource using this class's package using the
getClassLoader().getResourceAsStream() method. If this class was loaded
using the system classloader, ClassLoader.getSystemResource() is used
instead.
If the name you supply is absolute (it starts with a
/
),
then the leading
/
is removed and it is passed on to
getResource(). If it is relative, the package name is prepended, and
.
's are replaced with
/
.
The URL returned is system- and classloader-dependent, and could
change across implementations.
resourceName
- the name of the resource, generally a path
- an InputStream with the contents of the resource in it, or null
getSigners
public Object[] getSigners()
Get the signers of this class. This returns null if there are no signers,
such as for primitive types or void.
- the signers of this class
getSuperclass
public Class getSuperclass()
Get the direct superclass of this class. If this is an interface,
Object, a primitive type, or void, it will return null. If this is an
array type, it will return Object.
- the direct superclass of this class
isArray
public boolean isArray()
Return whether this class is an array type.
- whether this class is an array type
isAssignableFrom
public boolean isAssignableFrom(Class c)
Discover whether an instance of the Class parameter would be an
instance of this Class as well. Think of doing
isInstance(c.newInstance())
or even
c.newInstance() instanceof (this class)
. While this
checks widening conversions for objects, it must be exact for primitive
types.
- whether an instance of c would be an instance of this class
as well
isInstance
public boolean isInstance(Object o)
Discover whether an Object is an instance of this Class. Think of it
as almost like o instanceof (this class)
.
- whether o is an instance of this class
isInterface
public boolean isInterface()
Check whether this class is an interface or not. Array types are not
interfaces.
- whether this class is an interface or not
isPrimitive
public boolean isPrimitive()
Return whether this class is a primitive type. A primitive type class
is a class representing a kind of "placeholder" for the various
primitive types, or void. You can access the various primitive type
classes through java.lang.Boolean.TYPE, java.lang.Integer.TYPE, etc.,
or through boolean.class, int.class, etc.
- whether this class is a primitive type
newInstance
public Object newInstance()
throws InstantiationException,
IllegalAccessException
Get a new instance of this class by calling the no-argument constructor.
The class is initialized if it has not been already. A security check
may be performed, with checkMemberAccess(this, Member.PUBLIC)
as well as checkPackageAccess
both having to succeed.
- a new instance of this class
InstantiationException
- if there is not a no-arg constructor
for this class, including interfaces, abstract classes, arrays,
primitive types, and void; or if an exception occurred during
the constructorIllegalAccessException
- if you are not allowed to access the
no-arg constructor because of scoping reasonsSecurityException
- if the security check fails
toString
public String toString()
Return the human-readable form of this Object. For an object, this
is either "interface " or "class " followed by getName()
,
for primitive types and void it is just getName()
.
- toString in interface Object
- the human-readable form of this Object
Class.java -- Representation of a Java class.
Copyright (C) 1998, 1999, 2000, 2002, 2003, 2004, 2005
Free Software Foundation
This file is part of GNU Classpath.
GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.
GNU Classpath is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with GNU Classpath; see the file COPYING. If not, write to the
Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301 USA.
Linking this library statically or dynamically with other modules is
making a combined work based on this library. Thus, the terms and
conditions of the GNU General Public License cover the whole
combination.
As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
modules, and to copy and distribute the resulting executable under
terms of your choice, provided that you also meet, for each linked
independent module, the terms and conditions of the license of that
module. An independent module is a module which is not derived from
or based on this library. If you modify this library, you may extend
this exception to your version of the library, but you are not
obligated to do so. If you do not wish to do so, delete this
exception statement from your version.