Instances of the class {@code 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 {@code Class} object
that is shared by all arrays with the same element type and number
of dimensions. The primitive Java types ({@code boolean},
{@code byte}, {@code char}, {@code short},
{@code int}, {@code long}, {@code float}, and
{@code double}), and the keyword {@code void} are also
represented as {@code Class} objects.
{@code Class} has no public constructor. Instead {@code Class}
objects are constructed automatically by the Java Virtual Machine as classes
are loaded and by calls to the {@code defineClass} method in the class
loader.
The following example uses a {@code Class} object to print the
class name of an object:
It is also possible to get the {@code 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:
Method from java.lang.Class Detail: |
public Class<? extends U> asSubclass(Class<U> clazz) {
if (clazz.isAssignableFrom(this))
return (Class< ? extends U >) this;
else
throw new ClassCastException(this.toString());
}
Casts this {@code Class} object to represent a subclass of the class
represented by the specified class object. Checks that that the cast
is valid, and throws a {@code 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 {@code Class} object to pass it to an API that restricts the
{@code 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). |
public T cast(Object obj) {
if (obj != null && !isInstance(obj))
throw new ClassCastException(cannotCastMsg(obj));
return (T) obj;
}
Casts an object to the class or interface represented
by this {@code Class} object. |
public boolean desiredAssertionStatus() {
ClassLoader loader = getClassLoader();
// If the loader is null this is a system class, so ask the VM
if (loader == null)
return desiredAssertionStatus0(this);
// If the classloader has been initialized with the assertion
// directives, ask it. Otherwise, ask the VM.
synchronized(loader.assertionLock) {
if (loader.classAssertionStatus != null) {
return loader.desiredAssertionStatus(getName());
}
}
return desiredAssertionStatus0(this);
}
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. |
Map<String, T> enumConstantDirectory() {
if (enumConstantDirectory == null) {
T[] universe = getEnumConstantsShared();
if (universe == null)
throw new IllegalArgumentException(
getName() + " is not an enum type");
Map< String, T > m = new HashMap< >(2 * universe.length);
for (T constant : universe)
m.put(((Enum< ? >)constant).name(), constant);
enumConstantDirectory = m;
}
return enumConstantDirectory;
}
Returns a map from simple name to enum constant. This package-private
method is used internally by Enum to implement
public static > T valueOf(Class, String)
efficiently. Note that the map is returned by this method is
created lazily on first use. Typically it won't ever get created. |
public static Class<?> forName(String className) throws ClassNotFoundException {
return forName0(className, true, ClassLoader.getCallerClassLoader());
}
Returns the {@code Class} object associated with the class or
interface with the given string name. Invoking this method is
equivalent to:
{@code Class.forName(className, true, currentLoader)}
where {@code currentLoader} denotes the defining class loader of
the current class.
For example, the following code fragment returns the
runtime {@code Class} descriptor for the class named
{@code java.lang.Thread}:
{@code Class t = Class.forName("java.lang.Thread")}
A call to {@code forName("X")} causes the class named
{@code X} to be initialized. |
public static Class<?> forName(String name,
boolean initialize,
ClassLoader loader) throws ClassNotFoundException {
if (loader == null) {
SecurityManager sm = System.getSecurityManager();
if (sm != null) {
ClassLoader ccl = ClassLoader.getCallerClassLoader();
if (ccl != null) {
sm.checkPermission(
SecurityConstants.GET_CLASSLOADER_PERMISSION);
}
}
}
return forName0(name, initialize, loader);
}
Returns the {@code 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 {@code 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
{@code loader} is null, the class is loaded through the bootstrap
class loader. The class is initialized only if the
{@code initialize} parameter is {@code true} and if it has
not been initialized earlier.
If {@code 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 {@code name}. Therefore, this method cannot be used to
obtain any of the {@code Class} objects representing primitive
types or void.
If {@code 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:
{@code Class.forName("Foo")}
is equivalent to:
{@code 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 {@code loader} is {@code null}, and a security
manager is present, and the caller's class loader is not null, then this
method calls the security manager's {@code checkPermission} method
with a {@code RuntimePermission("getClassLoader")} permission to
ensure it's ok to access the bootstrap class loader. |
public A getAnnotation(Class<A> annotationClass) {
if (annotationClass == null)
throw new NullPointerException();
initAnnotationsIfNecessary();
return (A) annotations.get(annotationClass);
}
|
AnnotationType getAnnotationType() {
return annotationType;
}
|
public Annotation[] getAnnotations() {
initAnnotationsIfNecessary();
return AnnotationParser.toArray(annotations);
}
|
public String getCanonicalName() {
if (isArray()) {
String canonicalName = getComponentType().getCanonicalName();
if (canonicalName != null)
return canonicalName + "[]";
else
return null;
}
if (isLocalOrAnonymousClass())
return null;
Class< ? > enclosingClass = getEnclosingClass();
if (enclosingClass == null) { // top level class
return getName();
} else {
String enclosingName = enclosingClass.getCanonicalName();
if (enclosingName == null)
return null;
return enclosingName + "." + getSimpleName();
}
}
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). |
public ClassLoader getClassLoader() {
ClassLoader cl = getClassLoader0();
if (cl == null)
return null;
SecurityManager sm = System.getSecurityManager();
if (sm != null) {
ClassLoader ccl = ClassLoader.getCallerClassLoader();
if (ccl != null && ccl != cl && !cl.isAncestor(ccl)) {
sm.checkPermission(SecurityConstants.GET_CLASSLOADER_PERMISSION);
}
}
return cl;
}
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 {@code checkPermission}
method with a {@code 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. |
native ClassLoader getClassLoader0()
|
public Class<?>[] getClasses() {
// be very careful not to change the stack depth of this
// checkMemberAccess call for security reasons
// see java.lang.SecurityManager.checkMemberAccess
checkMemberAccess(Member.PUBLIC, ClassLoader.getCallerClassLoader());
// Privileged so this implementation can look at DECLARED classes,
// something the caller might not have privilege to do. The code here
// is allowed to look at DECLARED classes because (1) it does not hand
// out anything other than public members and (2) public member access
// has already been ok'd by the SecurityManager.
return java.security.AccessController.doPrivileged(
new java.security.PrivilegedAction< Class< ? >[] >() {
public Class[] run() {
List< Class< ? > > list = new ArrayList< >();
Class< ? > currentClass = Class.this;
while (currentClass != null) {
Class< ? >[] members = currentClass.getDeclaredClasses();
for (int i = 0; i < members.length; i++) {
if (Modifier.isPublic(members[i].getModifiers())) {
list.add(members[i]);
}
}
currentClass = currentClass.getSuperclass();
}
return list.toArray(new Class[0]);
}
});
}
Returns an array containing {@code Class} objects representing all
the public classes and interfaces that are members of the class
represented by this {@code 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 {@code Class} object has no public member
classes or interfaces. This method also returns an array of length 0 if
this {@code Class} object represents a primitive type, an array
class, or void. |
public native Class<?> getComponentType()
Returns the {@code Class} representing the component type of an
array. If this class does not represent an array class this method
returns null. |
native ConstantPool getConstantPool()
|
public Constructor<T> getConstructor(Class<?> parameterTypes) throws NoSuchMethodException, SecurityException {
// be very careful not to change the stack depth of this
// checkMemberAccess call for security reasons
// see java.lang.SecurityManager.checkMemberAccess
checkMemberAccess(Member.PUBLIC, ClassLoader.getCallerClassLoader());
return getConstructor0(parameterTypes, Member.PUBLIC);
}
Returns a {@code Constructor} object that reflects the specified
public constructor of the class represented by this {@code Class}
object. The {@code parameterTypes} parameter is an array of
{@code Class} objects that identify the constructor's formal
parameter types, in declared order.
If this {@code 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 {@code Class} object whose formal parameter
types match those specified by {@code parameterTypes}. |
public Constructor<?>[] getConstructors() throws SecurityException {
// be very careful not to change the stack depth of this
// checkMemberAccess call for security reasons
// see java.lang.SecurityManager.checkMemberAccess
checkMemberAccess(Member.PUBLIC, ClassLoader.getCallerClassLoader());
return copyConstructors(privateGetDeclaredConstructors(true));
}
Returns an array containing {@code Constructor} objects reflecting
all the public constructors of the class represented by this
{@code 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 {@code
Constructor} objects (that is an array of constructors from
this class), the return type of this method is {@code
Constructor>[]} and not {@code Constructor[]} 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 {@code Constructor} objects for
different classes, which would violate the type guarantees of
{@code Constructor[]}. |
public Annotation[] getDeclaredAnnotations() {
initAnnotationsIfNecessary();
return AnnotationParser.toArray(declaredAnnotations);
}
|
public Class<?>[] getDeclaredClasses() throws SecurityException {
// be very careful not to change the stack depth of this
// checkMemberAccess call for security reasons
// see java.lang.SecurityManager.checkMemberAccess
checkMemberAccess(Member.DECLARED, ClassLoader.getCallerClassLoader());
return getDeclaredClasses0();
}
Returns an array of {@code Class} objects reflecting all the
classes and interfaces declared as members of the class represented by
this {@code 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 {@code Class} object represents a
primitive type, an array class, or void. |
public Constructor<T> getDeclaredConstructor(Class<?> parameterTypes) throws NoSuchMethodException, SecurityException {
// be very careful not to change the stack depth of this
// checkMemberAccess call for security reasons
// see java.lang.SecurityManager.checkMemberAccess
checkMemberAccess(Member.DECLARED, ClassLoader.getCallerClassLoader());
return getConstructor0(parameterTypes, Member.DECLARED);
}
Returns a {@code Constructor} object that reflects the specified
constructor of the class or interface represented by this
{@code Class} object. The {@code parameterTypes} parameter is
an array of {@code Class} objects that identify the constructor's
formal parameter types, in declared order.
If this {@code 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. |
public Constructor<?>[] getDeclaredConstructors() throws SecurityException {
// be very careful not to change the stack depth of this
// checkMemberAccess call for security reasons
// see java.lang.SecurityManager.checkMemberAccess
checkMemberAccess(Member.DECLARED, ClassLoader.getCallerClassLoader());
return copyConstructors(privateGetDeclaredConstructors(false));
}
Returns an array of {@code Constructor} objects reflecting all the
constructors declared by the class represented by this
{@code 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 {@code Class}
object represents an interface, a primitive type, an array class, or
void.
See The Java Language Specification, section 8.2. |
public Field getDeclaredField(String name) throws NoSuchFieldException, SecurityException {
// be very careful not to change the stack depth of this
// checkMemberAccess call for security reasons
// see java.lang.SecurityManager.checkMemberAccess
checkMemberAccess(Member.DECLARED, ClassLoader.getCallerClassLoader());
Field field = searchFields(privateGetDeclaredFields(false), name);
if (field == null) {
throw new NoSuchFieldException(name);
}
return field;
}
Returns a {@code Field} object that reflects the specified declared
field of the class or interface represented by this {@code Class}
object. The {@code name} parameter is a {@code String} that
specifies the simple name of the desired field. Note that this method
will not reflect the {@code length} field of an array class. |
public Field[] getDeclaredFields() throws SecurityException {
// be very careful not to change the stack depth of this
// checkMemberAccess call for security reasons
// see java.lang.SecurityManager.checkMemberAccess
checkMemberAccess(Member.DECLARED, ClassLoader.getCallerClassLoader());
return copyFields(privateGetDeclaredFields(false));
}
Returns an array of {@code Field} objects reflecting all the fields
declared by the class or interface represented by this
{@code Class} object. This includes public, protected, default
(package) access, and private fields, but excludes inherited fields.
The elements in the array returned are not sorted and are not in any
particular order. This method returns an array of length 0 if the class
or interface declares no fields, or if this {@code Class} object
represents a primitive type, an array class, or void.
See The Java Language Specification, sections 8.2 and 8.3. |
public Method getDeclaredMethod(String name,
Class<?> parameterTypes) throws NoSuchMethodException, SecurityException {
// be very careful not to change the stack depth of this
// checkMemberAccess call for security reasons
// see java.lang.SecurityManager.checkMemberAccess
checkMemberAccess(Member.DECLARED, ClassLoader.getCallerClassLoader());
Method method = searchMethods(privateGetDeclaredMethods(false), name, parameterTypes);
if (method == null) {
throw new NoSuchMethodException(getName() + "." + name + argumentTypesToString(parameterTypes));
}
return method;
}
Returns a {@code Method} object that reflects the specified
declared method of the class or interface represented by this
{@code Class} object. The {@code name} parameter is a
{@code String} that specifies the simple name of the desired
method, and the {@code parameterTypes} parameter is an array of
{@code 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 {@code NoSuchMethodException}
is raised. |
public Method[] getDeclaredMethods() throws SecurityException {
// be very careful not to change the stack depth of this
// checkMemberAccess call for security reasons
// see java.lang.SecurityManager.checkMemberAccess
checkMemberAccess(Member.DECLARED, ClassLoader.getCallerClassLoader());
return copyMethods(privateGetDeclaredMethods(false));
}
|
public native Class<?> getDeclaringClass()
If the class or interface represented by this {@code Class} object
is a member of another class, returns the {@code 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 {@code Class} object represents an array class, a primitive
type, or void,then this method returns null. |
public Class<?> getEnclosingClass() {
// There are five kinds of classes (or interfaces):
// a) Top level classes
// b) Nested classes (static member classes)
// c) Inner classes (non-static member classes)
// d) Local classes (named classes declared within a method)
// e) Anonymous classes
// JVM Spec 4.8.6: A class must have an EnclosingMethod
// attribute if and only if it is a local class or an
// anonymous class.
EnclosingMethodInfo enclosingInfo = getEnclosingMethodInfo();
if (enclosingInfo == null) {
// This is a top level or a nested class or an inner class (a, b, or c)
return getDeclaringClass();
} else {
Class< ? > enclosingClass = enclosingInfo.getEnclosingClass();
// This is a local class or an anonymous class (d or e)
if (enclosingClass == this || enclosingClass == null)
throw new InternalError("Malformed enclosing method information");
else
return enclosingClass;
}
}
Returns the immediately enclosing class of the underlying
class. If the underlying class is a top level class this
method returns {@code null}. |
public Constructor<?> getEnclosingConstructor() {
EnclosingMethodInfo enclosingInfo = getEnclosingMethodInfo();
if (enclosingInfo == null)
return null;
else {
if (!enclosingInfo.isConstructor())
return null;
ConstructorRepository typeInfo = ConstructorRepository.make(enclosingInfo.getDescriptor(),
getFactory());
Type [] parameterTypes = typeInfo.getParameterTypes();
Class< ? >[] parameterClasses = new Class< ? >[parameterTypes.length];
// Convert Types to Classes; returned types *should*
// be class objects since the methodDescriptor's used
// don't have generics information
for(int i = 0; i < parameterClasses.length; i++)
parameterClasses[i] = toClass(parameterTypes[i]);
/*
* Loop over all declared constructors; match number
* of and type of parameters.
*/
for(Constructor< ? > c: enclosingInfo.getEnclosingClass().getDeclaredConstructors()) {
Class< ? >[] candidateParamClasses = c.getParameterTypes();
if (candidateParamClasses.length == parameterClasses.length) {
boolean matches = true;
for(int i = 0; i < candidateParamClasses.length; i++) {
if (!candidateParamClasses[i].equals(parameterClasses[i])) {
matches = false;
break;
}
}
if (matches)
return c;
}
}
throw new InternalError("Enclosing constructor not found");
}
}
If this {@code 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 {@code null} otherwise. In particular, this
method returns {@code null} if the underlying class is a local
or anonymous class immediately enclosed by a type declaration,
instance initializer or static initializer. |
public Method getEnclosingMethod() {
EnclosingMethodInfo enclosingInfo = getEnclosingMethodInfo();
if (enclosingInfo == null)
return null;
else {
if (!enclosingInfo.isMethod())
return null;
MethodRepository typeInfo = MethodRepository.make(enclosingInfo.getDescriptor(),
getFactory());
Class< ? > returnType = toClass(typeInfo.getReturnType());
Type [] parameterTypes = typeInfo.getParameterTypes();
Class< ? >[] parameterClasses = new Class< ? >[parameterTypes.length];
// Convert Types to Classes; returned types *should*
// be class objects since the methodDescriptor's used
// don't have generics information
for(int i = 0; i < parameterClasses.length; i++)
parameterClasses[i] = toClass(parameterTypes[i]);
/*
* Loop over all declared methods; match method name,
* number of and type of parameters, *and* return
* type. Matching return type is also necessary
* because of covariant returns, etc.
*/
for(Method m: enclosingInfo.getEnclosingClass().getDeclaredMethods()) {
if (m.getName().equals(enclosingInfo.getName()) ) {
Class< ? >[] candidateParamClasses = m.getParameterTypes();
if (candidateParamClasses.length == parameterClasses.length) {
boolean matches = true;
for(int i = 0; i < candidateParamClasses.length; i++) {
if (!candidateParamClasses[i].equals(parameterClasses[i])) {
matches = false;
break;
}
}
if (matches) { // finally, check return type
if (m.getReturnType().equals(returnType) )
return m;
}
}
}
}
throw new InternalError("Enclosing method not found");
}
}
If this {@code 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
{@code null} otherwise.
In particular, this method returns {@code null} if the underlying
class is a local or anonymous class immediately enclosed by a type
declaration, instance initializer or static initializer. |
public T[] getEnumConstants() {
T[] values = getEnumConstantsShared();
return (values != null) ? values.clone() : null;
}
Returns the elements of this enum class or null if this
Class object does not represent an enum type. |
T[] getEnumConstantsShared() {
if (enumConstants == null) {
if (!isEnum()) return null;
try {
final Method values = getMethod("values");
java.security.AccessController.doPrivileged(
new java.security.PrivilegedAction< Void >() {
public Void run() {
values.setAccessible(true);
return null;
}
});
enumConstants = (T[])values.invoke(null);
}
// These can happen when users concoct enum-like classes
// that don't comply with the enum spec.
catch (InvocationTargetException ex) { return null; }
catch (NoSuchMethodException ex) { return null; }
catch (IllegalAccessException ex) { return null; }
}
return enumConstants;
}
Returns the elements of this enum class or null if this
Class object does not represent an enum type;
identical to getEnumConstants except that the result is
uncloned, cached, and shared by all callers. |
public Field getField(String name) throws NoSuchFieldException, SecurityException {
// be very careful not to change the stack depth of this
// checkMemberAccess call for security reasons
// see java.lang.SecurityManager.checkMemberAccess
checkMemberAccess(Member.PUBLIC, ClassLoader.getCallerClassLoader());
Field field = getField0(name);
if (field == null) {
throw new NoSuchFieldException(name);
}
return field;
}
Returns a {@code Field} object that reflects the specified public
member field of the class or interface represented by this
{@code Class} object. The {@code name} parameter is a
{@code 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 represented by this object:
- If C declares a public field with the name specified, that is the
field to be reflected.
- If no field was found in step 1 above, this algorithm is applied
recursively to each direct superinterface of C. The direct
superinterfaces are searched in the order they were declared.
- If no field was found in steps 1 and 2 above, and C has a
superclass S, then this algorithm is invoked recursively upon S.
If C has no superclass, then a {@code NoSuchFieldException}
is thrown.
See The Java Language Specification, sections 8.2 and 8.3. |
public Field[] getFields() throws SecurityException {
// be very careful not to change the stack depth of this
// checkMemberAccess call for security reasons
// see java.lang.SecurityManager.checkMemberAccess
checkMemberAccess(Member.PUBLIC, ClassLoader.getCallerClassLoader());
return copyFields(privateGetPublicFields(null));
}
Returns an array containing {@code Field} objects reflecting all
the accessible public fields of the class or interface represented by
this {@code Class} object. The elements in the array returned are
not sorted and are not in any particular order. This method returns an
array of length 0 if the class or interface has no accessible public
fields, or if it represents an array class, a primitive type, or void.
Specifically, if this {@code Class} object represents a class,
this method returns the public fields of this class and of all its
superclasses. If this {@code Class} object represents an
interface, this method returns the fields of this interface and of all
its superinterfaces.
The implicit length field for array class is not reflected by this
method. User code should use the methods of class {@code Array} to
manipulate arrays.
See The Java Language Specification, sections 8.2 and 8.3. |
public Type[] getGenericInterfaces() {
if (getGenericSignature() != null)
return getGenericInfo().getSuperInterfaces();
else
return getInterfaces();
}
Returns the {@code Type}s representing the interfaces
directly implemented by the class or interface represented by
this object.
If a superinterface is a parameterized type, the
{@code 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 {@code implements} clause of the declaration of the class
represented by this object. In the case of an array class, the
interfaces {@code Cloneable} and {@code 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
{@code 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. |
public Type getGenericSuperclass() {
if (getGenericSignature() != null) {
// Historical irregularity:
// Generic signature marks interfaces with superclass = Object
// but this API returns null for interfaces
if (isInterface())
return null;
return getGenericInfo().getSuperclass();
} else
return getSuperclass();
}
Returns the {@code Type} representing the direct superclass of
the entity (class, interface, primitive type or void) represented by
this {@code Class}.
If the superclass is a parameterized type, the {@code 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 {@code Class} represents either the {@code Object}
class, an interface, a primitive type, or void, then null is
returned. If this object represents an array class then the
{@code Class} object representing the {@code Object} class is
returned. |
public native 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 {@code implements} clause
of the declaration of the class represented by this object. For
example, given the declaration:
{@code class Shimmer implements FloorWax, DessertTopping { ... }}
suppose the value of {@code s} is an instance of
{@code Shimmer}; the value of the expression:
{@code s.getClass().getInterfaces()[0]}
is the {@code Class} object that represents interface
{@code FloorWax}; and the value of:
{@code s.getClass().getInterfaces()[1]}
is the {@code Class} object that represents interface
{@code 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 {@code 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. |
public Method getMethod(String name,
Class<?> parameterTypes) throws NoSuchMethodException, SecurityException {
// be very careful not to change the stack depth of this
// checkMemberAccess call for security reasons
// see java.lang.SecurityManager.checkMemberAccess
checkMemberAccess(Member.PUBLIC, ClassLoader.getCallerClassLoader());
Method method = getMethod0(name, parameterTypes);
if (method == null) {
throw new NoSuchMethodException(getName() + "." + name + argumentTypesToString(parameterTypes));
}
return method;
}
Returns a {@code Method} object that reflects the specified public
member method of the class or interface represented by this
{@code Class} object. The {@code name} parameter is a
{@code String} specifying the simple name of the desired method. The
{@code parameterTypes} parameter is an array of {@code Class}
objects that identify the method's formal parameter types, in declared
order. If {@code parameterTypes} is {@code null}, it is
treated as if it were an empty array.
If the {@code name} is "{@code };"or "{@code }" a
{@code NoSuchMethodException} is raised. Otherwise, the method to
be reflected is determined by the algorithm that follows. Let C be the
class represented by this object:
- C is searched for any matching methods. If no matching
method is found, the algorithm of step 1 is invoked recursively on
the superclass of C.
- If no method was found in step 1 above, the superinterfaces of C
are searched for a matching method. If any such method is found, it
is reflected.
To find a matching method in a class C: If C declares exactly one
public method with the specified name and exactly the same formal
parameter types, that is the method reflected. If more than one such
method is found in C, and one of these methods has a return type that is
more specific than any of the others, that 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 {@linkplain
java.lang.reflect.Method#isBridge bridge methods}; the bridge
method and the method being overridden would have the same
signature but different return types.
See The Java Language Specification, sections 8.2 and 8.4. |
public Method[] getMethods() throws SecurityException {
// be very careful not to change the stack depth of this
// checkMemberAccess call for security reasons
// see java.lang.SecurityManager.checkMemberAccess
checkMemberAccess(Member.PUBLIC, ClassLoader.getCallerClassLoader());
return copyMethods(privateGetPublicMethods());
}
Returns an array containing {@code Method} objects reflecting all
the public member methods of the class or interface represented
by this {@code Class} object, including those declared by the class
or interface and those inherited from superclasses and
superinterfaces. Array classes return all the (public) member methods
inherited from the {@code Object} class. The elements in the array
returned are not sorted and are not in any particular order. This
method returns an array of length 0 if this {@code Class} object
represents a class or interface that has no public member methods, or if
this {@code Class} object represents a primitive type or void.
The class initialization method {@code } is not
included in the returned array. If the class declares multiple public
member methods with the same parameter types, they are all included in
the returned array.
See The Java Language Specification, sections 8.2 and 8.4. |
public native 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 {@code public}, {@code protected},
{@code private}, {@code final}, {@code static},
{@code abstract} and {@code interface}; they should be decoded
using the methods of class {@code Modifier}.
If the underlying class is an array class, then its
{@code public}, {@code private} and {@code protected}
modifiers are the same as those of its component type. If this
{@code Class} represents a primitive type or void, its
{@code public} modifier is always {@code true}, and its
{@code protected} and {@code private} modifiers are always
{@code false}. If this object represents an array class, a
primitive type or void, then its {@code final} modifier is always
{@code true} and its interface modifier is always
{@code 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. |
public String getName() {
String name = this.name;
if (name == null)
this.name = name = getName0();
return name;
}
Returns the name of the entity (class, interface, array class,
primitive type, or void) represented by this {@code Class} object,
as a {@code 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 {@code 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 '{@code [}' 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"
|
public Package getPackage() {
return Package.getPackage(this);
}
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. |
static native Class getPrimitiveClass(String name)
|
public ProtectionDomain getProtectionDomain() {
SecurityManager sm = System.getSecurityManager();
if (sm != null) {
sm.checkPermission(SecurityConstants.GET_PD_PERMISSION);
}
java.security.ProtectionDomain pd = getProtectionDomain0();
if (pd == null) {
if (allPermDomain == null) {
java.security.Permissions perms =
new java.security.Permissions();
perms.add(SecurityConstants.ALL_PERMISSION);
allPermDomain =
new java.security.ProtectionDomain(null, perms);
}
pd = allPermDomain;
}
return pd;
}
Returns the {@code ProtectionDomain} of this class. If there is a
security manager installed, this method first calls the security
manager's {@code checkPermission} method with a
{@code RuntimePermission("getProtectionDomain")} permission to
ensure it's ok to get the
{@code ProtectionDomain}. |
public URL getResource(String name) {
name = resolveName(name);
ClassLoader cl = getClassLoader0();
if (cl==null) {
// A system class.
return ClassLoader.getSystemResource(name);
}
return cl.getResource(name);
}
Finds a resource with a given name. The rules for searching resources
associated with a given class are implemented by the defining
{@linkplain ClassLoader 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 .
Before delegation, an absolute resource name is constructed from the
given resource name using this algorithm:
|
public InputStream getResourceAsStream(String name) {
name = resolveName(name);
ClassLoader cl = getClassLoader0();
if (cl==null) {
// A system class.
return ClassLoader.getSystemResourceAsStream(name);
}
return cl.getResourceAsStream(name);
}
Finds a resource with a given name. The rules for searching resources
associated with a given class are implemented by the defining
{@linkplain ClassLoader 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 .
Before delegation, an absolute resource name is constructed from the
given resource name using this algorithm:
|
public native Object[] getSigners()
Gets the signers of this class. |
public String getSimpleName() {
if (isArray())
return getComponentType().getSimpleName()+"[]";
String simpleName = getSimpleBinaryName();
if (simpleName == null) { // top level class
simpleName = getName();
return simpleName.substring(simpleName.lastIndexOf(".")+1); // strip the package name
}
// According to JLS3 "Binary Compatibility" (13.1) the binary
// name of non-package classes (not top level) is the binary
// name of the immediately enclosing class followed by a '$' followed by:
// (for nested and inner classes): the simple name.
// (for local classes): 1 or more digits followed by the simple name.
// (for anonymous classes): 1 or more digits.
// Since getSimpleBinaryName() will strip the binary name of
// the immediatly enclosing class, we are now looking at a
// string that matches the regular expression "\$[0-9]*"
// followed by a simple name (considering the simple of an
// anonymous class to be the empty string).
// Remove leading "\$[0-9]*" from the name
int length = simpleName.length();
if (length < 1 || simpleName.charAt(0) != '$')
throw new InternalError("Malformed class name");
int index = 1;
while (index < length && isAsciiDigit(simpleName.charAt(index)))
index++;
// Eventually, this is the empty string iff this is an anonymous class
return simpleName.substring(index);
}
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 "[]". |
public native Class<? super T> getSuperclass()
Returns the {@code Class} representing the superclass of the entity
(class, interface, primitive type or void) represented by this
{@code Class}. If this {@code Class} represents either the
{@code Object} class, an interface, a primitive type, or void, then
null is returned. If this object represents an array class then the
{@code Class} object representing the {@code Object} class is
returned. |
public TypeVariable<T>[] getTypeParameters() {
if (getGenericSignature() != null)
return (TypeVariable< Class< T > >[])getGenericInfo().getTypeParameters();
else
return (TypeVariable< Class< T > >[])new TypeVariable< ? >[0];
}
Returns an array of {@code TypeVariable} objects that represent the
type variables declared by the generic declaration represented by this
{@code GenericDeclaration} object, in declaration order. Returns an
array of length 0 if the underlying generic declaration declares no type
variables. |
public boolean isAnnotation() {
return (getModifiers() & ANNOTATION) != 0;
}
Returns true if this {@code 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. |
public boolean isAnnotationPresent(Class<Annotation> annotationClass) {
if (annotationClass == null)
throw new NullPointerException();
return getAnnotation(annotationClass) != null;
}
|
public boolean isAnonymousClass() {
return "".equals(getSimpleName());
}
Returns {@code true} if and only if the underlying class
is an anonymous class. |
public native boolean isArray()
Determines if this {@code Class} object represents an array class. |
public native boolean isAssignableFrom(Class<?> cls)
Determines if the class or interface represented by this
{@code Class} object is either the same as, or is a superclass or
superinterface of, the class or interface represented by the specified
{@code Class} parameter. It returns {@code true} if so;
otherwise it returns {@code false}. If this {@code Class}
object represents a primitive type, this method returns
{@code true} if the specified {@code Class} parameter is
exactly this {@code Class} object; otherwise it returns
{@code false}.
Specifically, this method tests whether the type represented by the
specified {@code Class} parameter can be converted to the type
represented by this {@code 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. |
public boolean isEnum() {
// An enum must both directly extend java.lang.Enum and have
// the ENUM bit set; classes for specialized enum constants
// don't do the former.
return (this.getModifiers() & ENUM) != 0 &&
this.getSuperclass() == java.lang.Enum.class;
}
Returns true if and only if this class was declared as an enum in the
source code. |
public native boolean isInstance(Object obj)
Determines if the specified {@code Object} is assignment-compatible
with the object represented by this {@code Class}. This method is
the dynamic equivalent of the Java language {@code instanceof}
operator. The method returns {@code true} if the specified
{@code Object} argument is non-null and can be cast to the
reference type represented by this {@code Class} object without
raising a {@code ClassCastException.} It returns {@code false}
otherwise.
Specifically, if this {@code Class} object represents a
declared class, this method returns {@code true} if the specified
{@code Object} argument is an instance of the represented class (or
of any of its subclasses); it returns {@code false} otherwise. If
this {@code Class} object represents an array class, this method
returns {@code true} if the specified {@code Object} argument
can be converted to an object of the array class by an identity
conversion or by a widening reference conversion; it returns
{@code false} otherwise. If this {@code Class} object
represents an interface, this method returns {@code true} if the
class or any superclass of the specified {@code Object} argument
implements this interface; it returns {@code false} otherwise. If
this {@code Class} object represents a primitive type, this method
returns {@code false}. |
public native boolean isInterface()
Determines if the specified {@code Class} object represents an
interface type. |
public boolean isLocalClass() {
return isLocalOrAnonymousClass() && !isAnonymousClass();
}
Returns {@code true} if and only if the underlying class
is a local class. |
public boolean isMemberClass() {
return getSimpleBinaryName() != null && !isLocalOrAnonymousClass();
}
Returns {@code true} if and only if the underlying class
is a member class. |
public native boolean isPrimitive()
Determines if the specified {@code Class} object represents a
primitive type.
There are nine predefined {@code 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 {@code boolean}, {@code byte},
{@code char}, {@code short}, {@code int},
{@code long}, {@code float}, and {@code double}.
These objects may only be accessed via the following public static
final variables, and are the only {@code Class} objects for which
this method returns {@code true}. |
public boolean isSynthetic() {
return (getModifiers() & SYNTHETIC) != 0;
}
Returns {@code true} if this class is a synthetic class;
returns {@code false} otherwise. |
public T newInstance() throws InstantiationException, IllegalAccessException {
if (System.getSecurityManager() != null) {
checkMemberAccess(Member.PUBLIC, ClassLoader.getCallerClassLoader());
}
return newInstance0();
}
Creates a new instance of the class represented by this {@code Class}
object. The class is instantiated as if by a {@code 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) java.lang.reflect.InvocationTargetException . |
void setAnnotationType(AnnotationType type) {
annotationType = type;
}
|
native void setProtectionDomain0(ProtectionDomain pd)
Set the ProtectionDomain for this class. Called by
ClassLoader.defineClass. |
native void setSigners(Object[] signers)
Set the signers of this class. |
public String toString() {
return (isInterface() ? "interface " : (isPrimitive() ? "" : "class "))
+ getName();
}
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
{@code getName}. If this {@code Class} object represents a
primitive type, this method returns the name of the primitive type. If
this {@code Class} object represents void this method returns
"void". |