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java.lang
Class Class<T> Class 


java.lang.Object
  extended by java.lang.Class
All Implemented Interfaces:
AnnotatedElement Serializable , GenericDeclaration , Serializable , Type
public final class Class<T> Class
extends Object
implements Serializable , GenericDeclaration , Type , AnnotatedElement

Instances of the class Class represent classes and interfaces in a running Java application. 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 (JLS Section 15.8.2 ). For example: 

     System.out.println("The name of class Foo is: "+Foo.class.getName());

Since:
JDK1.0
See Also:
ClassLoader.defineClass(byte[], int, int) , Serialized Form

Method Summary
  T cast ( Object
          Casts an object to the class or interface represented by this Class object.
 boolean desiredAssertionStatus ()
          Returns the assertion status that would be assigned to this class if it were to be initialized at the time this method is invoked.
static  Class forName ( String  className)
          Returns the Class object associated with the class or interface with the given string name.
static  Class forName ( String  name, boolean initialize, ClassLoader  loader)
          Returns the Class object associated with the class or interface with the given string name, using the given class loader.
<A extends java.lang.annotation.Annotation>
A
getAnnotation ( Class <A> annotationClass)
           
 java.lang.annotation.Annotation[] getAnnotations ()
          Returns all annotations present on this element.
  Class [] getClasses ()
          Returns an array containing Class objects representing all the public classes and interfaces that are members of the class represented by this Class object.
  ClassLoader getClassLoader ()
          Returns the class loader for the class.
  Class getComponentType ()
          Returns the Class representing the component type of an array.
  Constructor < T getConstructor getConstructor ( Class
          Returns a Constructor object that reflects the specified public constructor of the class represented by this Class object.
  Constructor [] getConstructors ()
          Returns an array containing Constructor objects reflecting all the public constructors of the class represented by this Class object.
 java.lang.annotation.Annotation[] getDeclaredAnnotations ()
          Returns all annotations that are directly present on this element.
  Class [] getDeclaredClasses ()
          Returns an array of Class objects reflecting all the classes and interfaces declared as members of the class represented by this Class object.
  Constructor < T getDeclaredConstructor getDeclaredConstructor ( Class
          Returns a Constructor object that reflects the specified constructor of the class or interface represented by this Class object.
  Constructor [] getDeclaredConstructors ()
          Returns an array of Constructor objects reflecting all the constructors declared by the class represented by this Class object.
  Field getDeclaredField ( String  name)
          Returns a Field object that reflects the specified declared field of the class or interface represented by this Class object.
  Field [] getDeclaredFields ()
          Returns an array of Field objects reflecting all the fields declared by the class or interface represented by this Class object.
  Method getDeclaredMethod getDeclaredMethod ( String  name, Class
          Returns a Method object that reflects the specified declared method of the class or interface represented by this Class object.
  Method [] getDeclaredMethods ()
          Returns an array of Method objects reflecting all the methods declared by the class or interface represented by this Class object.
  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.
  Method getEnclosingConstructor ()
          If this Class object represents a local or anonymous class within a constructor, returns a Constructor
  Method getEnclosingMethod ()
          If this Class object represents a local or anonymous class within a method, returns a Method
  T getEnumConstants ()
          Returns the elements of this enum class or null if this Class object does not represent an enum type.
  Field getField ( String  name)
          Returns a Field object that reflects the specified public member field of the class or interface represented by this Class object.
  Field [] getFields ()
          Returns an array containing Field objects reflecting all the accessible public fields of the class or interface represented by this Class object.
  Type getGenericInterfaces ()
          Returns the Type <\tt> s representing the interfaces directly implemented by the class or interface represented by this object.
  Type getGenericSuperclass ()
          Returns the Type representing the direct superclass of the entity (class, interface, primitive type or void) represented by this Class .
  Class [] getInterfaces ()
          Determines the interfaces implemented by the class or interface represented by this object.
  Method getMethod getMethod ( String  name, Class
          Returns a Method object that reflects the specified public member method of the class or interface represented by this Class object.
  Method [] getMethods ()
          Returns an array containing Method objects reflecting all the public member methods of the class or interface represented by this Class object, including those declared by the class or interface and and those inherited from superclasses and superinterfaces.
 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 Class object, as a String .
  Package getPackage ()
          Gets the package for this class.
  ProtectionDomain getProtectionDomain ()
          Returns the ProtectionDomain of this class.
  URL getResource ( String  name)
          Finds a resource with a given name.
  InputStream getResourceAsStream ( String  name)
          Finds a resource with a given name.
  Object [] getSigners ()
          Gets the signers of this class.
  Class <? super T getSuperclass ()
          Returns the Class representing the superclass of the entity (class, interface, primitive type or void) represented by this Class.
  TypeVariable 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.
 boolean isAnnotationPresent ( Class
          Returns true if an annotation for the specified type is present on this element, else false.
 boolean isAnnotationType ()
          Returns true if this Class object represents an annotation type.
 boolean isArray ()
          Determines if this Class object represents an array class.
 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.
 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 Object is assignment-compatible with the object represented by this Class.
 boolean isInterface ()
          Determines if the specified Class object represents an interface type.
 boolean isPrimitive ()
          Determines if the specified Class object represents a primitive type.
  T Object newInstance ()
          Creates a new instance of the class represented by this Class object.
  String toString ()
          Converts the object to a string.
 
Methods inherited from class java.lang. Object
clone , equals , finalize , getClass , hashCode , notify , notifyAll , wait , wait , wait
 
Methods inherited from interface java.lang.reflect. AnnotatedElement
getAnnotation
 

Method Detail

toString


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".

Overrides:
toString in class Object
Returns:
a string representation of this class object.

forName


public static Class forName(String className)
                     throws ClassNotFoundException
Returns the Class object associated with the class or interface with the given string name. Invoking this method is equivalent to: 
  Class.forName(className, true, currentLoader)
where currentLoader denotes the defining class loader of the current class.

For example, the following code fragment returns the runtime Class descriptor for the class named java.lang.Thread: 

   Class t = Class.forName("java.lang.Thread")

A call to forName("X") causes the class named X to be initialized.

Parameters:
className - the fully qualified name of the desired class.
Returns:
the Class object for the class with the specified name.
Throws:
LinkageError - if the linkage fails
ExceptionInInitializerError - if the initialization provoked by this method fails
ClassNotFoundException - if the class cannot be located

forName


public static Class forName(String name,
                            boolean initialize,
                            ClassLoader loader)
                     throws ClassNotFoundException
Returns the Class object associated with the class or interface with the given string name, using the given class loader. Given the fully qualified name for a class or interface (in the same format returned by getName) this method attempts to locate, load, and link the class or interface. The specified class loader is used to load the class or interface. If the parameter loader is null, the class is loaded through the bootstrap class loader. The class is initialized only if the initialize parameter is true and if it has not been initialized earlier.

If name denotes a primitive type or void, an attempt will be made to locate a user-defined class in the unnamed package whose name is name. Therefore, this method cannot be used to obtain any of the Class objects representing primitive types or void.

If name denotes an array class, the component type of the array class is loaded but not initialized.

For example, in an instance method the expression: 

  Class.forName("Foo")
is equivalent to: 
  Class.forName("Foo", true, this.getClass().getClassLoader())
Note that this method throws errors related to loading, linking or initializing as specified in Sections 12.2, 12.3 and 12.4 of The Java Language Specification. Note that this method does not check whether the requested class is accessible to its caller.

If the loader is null, and a security manager is present, and the caller's class loader is not null, then this method calls the security manager's checkPermission method with a RuntimePermission("getClassLoader") permission to ensure it's ok to access the bootstrap class loader.

Parameters:
name - fully qualified name of the desired class
initialize - whether the class must be initialized
loader - class loader from which the class must be loaded
Returns:
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
Since:
1.2
See Also:
forName(String) , ClassLoader

newInstance


public TObjectnewInstance()
 throws InstantiationException,
 IllegalAccessException
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.

If there is a security manager, this method first calls the security manager's checkMemberAccess method with this and Member.PUBLIC as its arguments. If the class is in a package, then this method also calls the security manager's checkPackageAccess method with the package name as its argument. Either of these calls could result in a SecurityException.

Returns:
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 there is no permission to create a new instance.

isInstance


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 - the object to check
Returns:
true if obj is an instance of this class
Since:
JDK1.1

isAssignableFrom


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 - the Class object to be checked
Returns:
the boolean value indicating whether objects of the type cls can be assigned to objects of this class
Throws:
NullPointerException - if the specified Class parameter is null.
Since:
JDK1.1

isInterface


public boolean isInterface()
Determines if the specified Class object represents an interface type.

Returns:
true if this object represents an interface; false otherwise.

isArray


public boolean isArray()
Determines if this Class object represents an array class.

Returns:
true if this object represents an array class; false otherwise.
Since:
JDK1.1

isPrimitive


public boolean isPrimitive()
Determines if the specified Class object represents a primitive type.

There are nine predefined Class objects to represent the eight primitive types and void. These are created by the Java Virtual Machine, and have the same names as the primitive types that they represent, namely boolean, byte, char, short, int, long, float, and double.

These objects may only be accessed via the following public static final variables, and are the only Class objects for which this method returns true.

Returns:
true if and only if this class represents a primitive type
Since:
JDK1.1
See Also:
Boolean.TYPE , Character.TYPE , Byte.TYPE , Short.TYPE , Integer.TYPE , Long.TYPE , Float.TYPE , Double.TYPE , Void.TYPE

isAnnotationType 


 
public boolean isAnnotationType ()
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:
true if this class object represents an annotation type; false otherwise
Since:
1.5

getName


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, Second Edition.

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 L classname;
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:
the name of the class or interface represented by this object.

getClassLoader


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:
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.
See Also:
ClassLoader , SecurityManager.checkPermission(java.security.Permission) , RuntimePermission

getTypeParameters 


 
public TypeVariable[] getTypeParameters ()
Returns an array of TypeVariable objects that represent the type variables declared by the generic declaration represented by this GenericDeclaration object, in declaration order. Returns an array of length 0 if the underlying generic declaration declares no type variables.

Specified by:
getTypeParameters in interface GenericDeclaration
Returns:
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, 3rd edition
Since:
1.5

getSuperclass


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:
the superclass of the class represented by this object.

getGenericSuperclass 


 
public TypegetGenericSuperclass ()
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:
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, 3rd edition
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
Since:
1.5

getPackage


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:
the package of the class, or null if no package information is available from the archive or codebase.

getInterfaces


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.

Returns:
an array of interfaces implemented by this class.

getGenericInterfaces 


 
public Type[] getGenericInterfaces ()
Returns the Type <\tt> 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:
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, 3rd edition
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
Since:
1.5

getComponentType


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:
the Class representing the component type of this class if this class is an array
Since:
JDK1.1
See Also:
Array

getModifiers


public int getModifiers()
Returns the Java language modifiers for this class or interface, encoded in an integer. The modifiers consist of the Java Virtual Machine's constants for public, protected, private, final, static, abstract and interface; they should be decoded using the methods of class Modifier.

If the underlying class is an array class, then its public, private and protected modifiers are the same as those of its component type. 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:
the int representing the modifiers for this class
Since:
JDK1.1
See Also:
Modifier

getSigners


public Object[] getSigners()
Gets the signers of this class.

Returns:
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.
Since:
JDK1.1

getEnclosingMethod 


 
public MethodgetEnclosingMethod ()
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:
the immediately enclosing method of the underlying class, if that class is a local or anonymous class; otherwise null .
Since:
1.5

getEnclosingConstructor 


 
public MethodgetEnclosingConstructor ()
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:
the immediately enclosing method of the underlying class, if that class is a local or anonymous class; otherwise null .
Since:
1.5

getDeclaringClass


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:
the declaring class for this class
Since:
JDK1.1

getClasses


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.

For this class and each of its superclasses, the following security checks are performed: If there is a security manager, the security manager's checkMemberAccess method is called with this and Member.PUBLIC as its arguments, where this is this class or the superclass whose members are being determined. If the class is in a package, then the security manager's checkPackageAccess method is also called with the package name as its argument. Either of these calls could result in a SecurityException.

Returns:
the array of Class objects representing the public members of this class
Throws:
SecurityException - if access to the information is denied.
Since:
JDK1.1
See Also:
SecurityManager.checkMemberAccess(Class, int) , SecurityManager.checkPackageAccess(String)

getFields


public Field[] getFields()
                  throws SecurityException
Returns an array containing Field objects reflecting all the accessible public fields of the class or interface represented by this Class object. The elements in the array returned are not sorted and are not in any particular order. This method returns an array of length 0 if the class or interface has no accessible public fields, or if it represents an array class, a primitive type, or void.

Specifically, if this Class object represents a class, this method returns the public fields of this class and of all its superclasses. If this Class object represents an interface, this method returns the fields of this interface and of all its superinterfaces.

If there is a security manager, this method first calls the security manager's checkMemberAccess method with this and Member.PUBLIC as its arguments. If the class is in a package, then this method also calls the security manager's checkPackageAccess method with the package name as its argument. Either of these calls could result in a SecurityException.

The implicit length field for array class is not reflected by this method. User code should use the methods of class Array to manipulate arrays.

See The Java Language Specification, sections 8.2 and 8.3.

Returns:
the array of Field objects representing the public fields
Throws:
SecurityException - if access to the information is denied.
Since:
JDK1.1
See Also:
Field , SecurityManager.checkMemberAccess(Class, int) , SecurityManager.checkPackageAccess(String)

getMethods


public Method[] getMethods()
                    throws SecurityException
Returns an array containing Method objects reflecting all the public member methods of the class or interface represented by this Class object, including those declared by the class or interface and and those inherited from superclasses and superinterfaces. 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 Class object represents a class or interface that has no public member methods, or if this Class object represents an array class, primitive type, or void.

If there is a security manager, this method first calls the security manager's checkMemberAccess method with this and Member.PUBLIC as its arguments. If the class is in a package, then this method also calls the security manager's checkPackageAccess method with the package name as its argument. Either of these calls could result in a SecurityException.

The class initialization method <clinit> is not included in the returned array. If the class declares multiple public member methods with the same parameter types, they are all included in the returned array.

See The Java Language Specification, sections 8.2 and 8.4.

Returns:
the array of Method objects representing the public methods of this class
Throws:
SecurityException - if access to the information is denied.
Since:
JDK1.1
See Also:
Method , SecurityManager.checkMemberAccess(Class, int) , SecurityManager.checkPackageAccess(String)

getConstructors


public Constructor[] getConstructors()
                              throws SecurityException
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.

If there is a security manager, this method first calls the security manager's checkMemberAccess method with this and Member.PUBLIC as its arguments. If the class is in a package, then this method also calls the security manager's checkPackageAccess method with the package name as its argument. Either of these calls could result in a SecurityException.

Returns:
the array containing Method objects for all the declared public constructors of this class matches the specified parameterTypes
Throws:
SecurityException - if access to the information is denied.
Since:
JDK1.1
See Also:
Constructor , SecurityManager.checkMemberAccess(Class, int) , SecurityManager.checkPackageAccess(String)

getField


public Field getField(String name)
               throws NoSuchFieldException,
                      SecurityException
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.

If there is a security manager, this method first calls the security manager's checkMemberAccess method with this and Member.PUBLIC as its arguments. If the class is in a package, then this method also calls the security manager's checkPackageAccess method with the package name as its argument. Either of these calls could result in a SecurityException.

The field to be reflected is determined by the algorithm that follows. Let C be the class represented by this object:

  1. If C declares a public field with the name specified, that is the field to be reflected.
  2. 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.
  3. If no field was found in steps 1 and 2 above, and C has a superclass S, then this algorithm is invoked recursively upon S. If C has no superclass, then a NoSuchFieldException is thrown.

See The Java Language Specification, sections 8.2 and 8.3.

Parameters:
name - the field name
Returns:
the Field object of this class specified by name
Throws:
NoSuchFieldException - if a field with the specified name is not found.
NullPointerException - if name is null
SecurityException - if access to the information is denied.
Since:
JDK1.1
See Also:
Field , SecurityManager.checkMemberAccess(Class, int) , SecurityManager.checkPackageAccess(String)

getMethod


public MethodgetMethod(String name,
                        Class... parameterTypes)
 [] parameterTypes)
 throws NoSuchMethodException,
                        SecurityException
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 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 there is a security manager, this method first calls the security manager's checkMemberAccess method with this and Member.PUBLIC as its arguments. If the class is in a package, then this method also calls the security manager's checkPackageAccess method with the package name as its argument. Either of these calls could result in a SecurityException.

If the name is "<init>"or "<clinit>" a NoSuchMethodException is raised. Otherwise, the method to be reflected is determined by the algorithm that follows. Let C be the class represented by this object:

  1. 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.
  2. 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.

See The Java Language Specification, sections 8.2 and 8.4.

Parameters:
name - the name of the method
parameterTypes - the list of parameters
Returns:
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 access to the information is denied.
Since:
JDK1.1
See Also:
Method , SecurityManager.checkMemberAccess(Class, int) , SecurityManager.checkPackageAccess(String)

getConstructor


public Constructor< T> getConstructor(Class... parameterTypes)
 [] parameterTypes)
 throws NoSuchMethodException,
 SecurityException
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.

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.

If there is a security manager, this method first calls the security manager's checkMemberAccess method with this and Member.PUBLIC as its arguments. If the class is in a package, then this method also calls the security manager's checkPackageAccess method with the package name as its argument. Either of these calls could result in a SecurityException.

Parameters:
parameterTypes - the parameter array
Returns:
the Method object of the public constructor that matches the specified parameterTypes
Throws:
NoSuchMethodException - if a matching method is not found.
SecurityException - if access to the information is denied.
Since:
JDK1.1
See Also:
Constructor , SecurityManager.checkMemberAccess(Class, int) , SecurityManager.checkPackageAccess(String)

getDeclaredClasses


public Class[] getDeclaredClasses()
                           throws SecurityException
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.

If there is a security manager, this method first calls the security manager's checkMemberAccess method with this and Member.DECLARED as its arguments. If the class is in a package, then this method also calls the security manager's checkPackageAccess method with the package name as its argument. Either of these calls could result in a SecurityException.

Returns:
the array of Class objects representing all the declared members of this class
Throws:
SecurityException - if access to the information is denied.
Since:
JDK1.1
See Also:
SecurityManager.checkMemberAccess(Class, int) , SecurityManager.checkPackageAccess(String)

getDeclaredFields


public Field[] getDeclaredFields()
                          throws SecurityException
Returns an array of Field objects reflecting all the fields declared by the class or interface represented by this Class object. This includes public, protected, default (package) access, and private fields, but excludes inherited fields. The elements in the array returned are not sorted and are not in any particular order. This method returns an array of length 0 if the class or interface declares no fields, or if this Class object represents a primitive type, an array class, or void.

See The Java Language Specification, sections 8.2 and 8.3.

If there is a security manager, this method first calls the security manager's checkMemberAccess method with this and Member.DECLARED as its arguments. If the class is in a package, then this method also calls the security manager's checkPackageAccess method with the package name as its argument. Either of these calls could result in a SecurityException.

Returns:
the array of Field objects representing all the declared fields of this class
Throws:
SecurityException - if access to the information is denied.
Since:
JDK1.1
See Also:
Field , SecurityManager.checkMemberAccess(Class, int) , SecurityManager.checkPackageAccess(String)

getDeclaredMethods


public Method[] getDeclaredMethods()
                            throws SecurityException
Returns an array of Method objects reflecting all the methods declared by the class or interface represented by this Class object. This includes public, protected, default (package) access, and private methods, but excludes inherited methods. The elements in the array returned are not sorted and are not in any particular order. This method returns an array of length 0 if the class or interface declares no methods, or if this Class object represents a primitive type, an array class, or void. The class initialization method <clinit> is not included in the returned array. If the class declares multiple public member methods with the same parameter types, they are all included in the returned array.

See The Java Language Specification, section 8.2.

If there is a security manager, this method first calls the security manager's checkMemberAccess method with this and Member.DECLARED as its arguments. If the class is in a package, then this method also calls the security manager's checkPackageAccess method with the package name as its argument. Either of these calls could result in a SecurityException.

Returns:
the array of Method objects representing all the declared methods of this class
Throws:
SecurityException - if access to the information is denied.
Since:
JDK1.1
See Also:
Method , SecurityManager.checkMemberAccess(Class, int) , SecurityManager.checkPackageAccess(String)

getDeclaredConstructors


public Constructor[] getDeclaredConstructors()
                                      throws SecurityException
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.

If there is a security manager, this method first calls the security manager's checkMemberAccess method with this and Member.DECLARED as its arguments. If the class is in a package, then this method also calls the security manager's checkPackageAccess method with the package name as its argument. Either of these calls could result in a SecurityException.

Returns:
the array of Method objects representing all the declared constructors of this class
Throws:
SecurityException - if access to the information is denied.
Since:
JDK1.1
See Also:
Constructor , SecurityManager.checkMemberAccess(Class, int) , SecurityManager.checkPackageAccess(String)

getDeclaredField


public Field getDeclaredField(String name)
                       throws NoSuchFieldException,
                              SecurityException
Returns a Field object that reflects the specified declared field of the class or interface represented by this Class object. The name parameter is a String that specifies the simple name of the desired field. Note that this method will not reflect the length field of an array class.

If there is a security manager, this method first calls the security manager's checkMemberAccess method with this and Member.DECLARED as its arguments. If the class is in a package, then this method also calls the security manager's checkPackageAccess method with the package name as its argument. Either of these calls could result in a SecurityException.

Parameters:
name - the name of the field
Returns:
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 access to the information is denied.
Since:
JDK1.1
See Also:
Field , SecurityManager.checkMemberAccess(Class, int) , SecurityManager.checkPackageAccess(String)

getDeclaredMethod


public MethodgetDeclaredMethod(String name,
                                Class... parameterTypes)
 [] parameterTypes)
 throws NoSuchMethodException,
                                SecurityException
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 there is a security manager, this method first calls the security manager's checkMemberAccess method with this and Member.DECLARED as its arguments. If the class is in a package, then this method also calls the security manager's checkPackageAccess method with the package name as its argument. Either of these calls could result in a SecurityException.

Parameters:
name - the name of the method
parameterTypes - the parameter array
Returns:
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 access to the information is denied.
Since:
JDK1.1
See Also:
Method , SecurityManager.checkMemberAccess(Class, int) , SecurityManager.checkPackageAccess(String)

getDeclaredConstructor


public Constructor< T> getDeclaredConstructor(Class... parameterTypes)
 [] parameterTypes)
 throws NoSuchMethodException,
 SecurityException
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 there is a security manager, this method first calls the security manager's checkMemberAccess method with this and Member.DECLARED as its arguments. If the class is in a package, then this method also calls the security manager's checkPackageAccess method with the package name as its argument. Either of these calls could result in a SecurityException.

Parameters:
parameterTypes - the parameter array
Returns:
The Method object for the constructor with the specified parameter list
Throws:
NoSuchMethodException - if a matching method is not found.
SecurityException - if access to the information is denied.
Since:
JDK1.1
See Also:
Constructor , SecurityManager.checkMemberAccess(Class, int) , SecurityManager.checkPackageAccess(String)

getResourceAsStream


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(java.lang.String) . This method returns null if no resource with this name is found. The rules for searching resources associated with a given class are implemented by the defining class loader of the class.

Before delegation, an absolute resource name is constructed from the given resource name using this algorithm:

  • If the name begins with a '/' ( '\u002f' ), then the absolute name of the resource is the portion of the name following the '/' .
  • Otherwise, the absolute name is of the following form: 
    modified_package_name / name

    Where the modified_package_name is the package name of this object with '/' substituted for '.' ( '\u002e' ).

This method delegates the call to its class loader, after making these changes to the resource name: if the resource name starts with "/", it is unchanged; otherwise, the package name is prepended to the resource name after converting "." to "/". If this object was loaded by the bootstrap loader, the call is delegated to ClassLoader.getSystemResourceAsStream.

Parameters:
name - name of the desired resource
Returns:
A InputStream object or null if no resource with this name is found a java.io.InputStream object.
Throws:
NullPointerException - If name is null - if name is null.
Since:
JDK1.1
See Also:
ClassLoader

getResource


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(java.lang.String) . This method returns null if no resource with this name is found. The rules for searching resources associated with a given class are implemented by the * defining class loader of the class.

Before delegation, an absolute resource name is constructed from the given resource name using this algorithm:

  • If the name begins with a '/' ( '\u002f' ), then the absolute name of the resource is the portion of the name following the '/' .
  • Otherwise, the absolute name is of the following form: 
    modified_package_name / name

    Where the modified_package_name is the package name of this object with '/' substituted for '.' ( '\u002e'