java.lang.reflect

Class Method

java.lang.Object

java.lang.reflect.AccessibleObject

java.lang.reflect.Method

All Implemented Interfaces:

Member

public final class Method
extends AccessibleObject
implements Member

A Method provides information about, and access to, a single method on a class or interface. The reflected method may be a class method or an instance method (including an abstract method).

A Method permits widening conversions to occur when matching the actual parameters to invokewith the underlying method's formal parameters, but it throws an IllegalArgumentException if a narrowing conversion would occur.

Author:

Nakul Saraiya

See Also:

Member, Class, Class.getMethods(), Class.getMethod(String, Class[]), Class.getDeclaredMethods(), Class.getDeclaredMethod(String, Class[])

Field Summary

Fields inherited from interface java.lang.reflect.Member

DECLARED, PUBLIC

Method Summary

Methods

Modifier and Type	Method and Description
boolean	equals(Object obj) Compares this Method against the specified object.
Class	getDeclaringClass() Returns the Class object representing the class or interface that declares the method represented by this Method object.
Class[]	getExceptionTypes() Returns an array of Class objects that represent the types of the exceptions declared to be thrown by the underlying method represented by this Method object.
int	getModifiers() Returns the Java language modifiers for the method represented by this Method object, as an integer.
String	getName() Returns the name of the method represented by this Method object, as a String.
Class[]	getParameterTypes() Returns an array of Class objects that represent the formal parameter types, in declaration order, of the method represented by this Method object.
Class	getReturnType() Returns a Class object that represents the formal return type of the method represented by this Method object.
int	hashCode() Returns a hashcode for this Method.
Object	invoke(Object obj, Object[] args) Invokes the underlying method represented by this Method object, on the specified object with the specified parameters.
String	toString() Returns a string describing this Method.

Methods inherited from class java.lang.reflect.AccessibleObject

isAccessible, setAccessible, setAccessible

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Method Detail

getDeclaringClass

public Class getDeclaringClass()

Returns the Class object representing the class or interface that declares the method represented by this Method object.

Specified by:

getDeclaringClass in interface Member

Returns:

an object representing the declaring class of the underlying member

getName

public String getName()

Returns the name of the method represented by this Method object, as a String.

Specified by:

getName in interface Member

Returns:

the simple name of the underlying member

getModifiers

public int getModifiers()

Returns the Java language modifiers for the method represented by this Method object, as an integer. The Modifier class should be used to decode the modifiers.

Specified by:

getModifiers in interface Member

Returns:

the Java language modifiers for the underlying member

See Also:

Modifier

getReturnType

public Class getReturnType()

Returns a Class object that represents the formal return type of the method represented by this Method object.

Returns:

the return type for the method this object represents

getParameterTypes

public Class[] getParameterTypes()

Returns an array of Class objects that represent the formal parameter types, in declaration order, of the method represented by this Method object. Returns an array of length 0 if the underlying method takes no parameters.

Returns:

the parameter types for the method this object represents

getExceptionTypes

public Class[] getExceptionTypes()

Returns an array of Class objects that represent the types of the exceptions declared to be thrown by the underlying method represented by this Method object. Returns an array of length 0 if the method declares no exceptions in its throws clause.

Returns:

the exception types declared as being thrown by the method this object represents

equals

public boolean equals(Object obj)

Compares this Method against the specified object. Returns true if the objects are the same. Two Methods are the same if they were declared by the same class and have the same name and formal parameter types and return type.

Overrides:

equals in class Object

Parameters:

obj - the reference object with which to compare.

Returns:

true if this object is the same as the obj argument; false otherwise.

See Also:

Object.hashCode(), Hashtable

hashCode

public int hashCode()

Returns a hashcode for this Method. The hashcode is computed as the exclusive-or of the hashcodes for the underlying method's declaring class name and the method's name.

Overrides:

hashCode in class Object

Returns:

a hash code value for this object.

See Also:

Object.equals(java.lang.Object), Hashtable

toString

public String toString()

Returns a string describing this Method. The string is formatted as the method access modifiers, if any, followed by the method return type, followed by a space, followed by the class declaring the method, followed by a period, followed by the method name, followed by a parenthesized, comma-separated list of the method's formal parameter types. If the method throws checked exceptions, the parameter list is followed by a space, followed by the word throws followed by a comma-separated list of the thrown exception types. For example:

    public boolean java.lang.Object.equals(java.lang.Object)
 

The access modifiers are placed in canonical order as specified by "The Java Language Specification". This is public, protected or private first, and then other modifiers in the following order: abstract, static, final, synchronized native.

Overrides:

toString in class Object

Returns:

a string representation of the object.

invoke

public Object invoke(Object obj,
            Object[] args)
              throws IllegalAccessException,
                     IllegalArgumentException,
                     InvocationTargetException

Invokes the underlying method represented by this Method object, on the specified object with the specified parameters. Individual parameters are automatically unwrapped to match primitive formal parameters, and both primitive and reference parameters are subject to method invocation conversions as necessary.

If the underlying method is static, then the specified obj argument is ignored. It may be null.

If the number of formal parameters required by the underlying method is 0, the supplied args array may be of length 0 or null.

If the underlying method is an instance method, it is invoked using dynamic method lookup as documented in The Java Language Specification, Second Edition, section 15.12.4.4; in particular, overriding based on the runtime type of the target object will occur.

If the underlying method is static, the class that declared the method is initialized if it has not already been initialized.

If the method completes normally, the value it returns is returned to the caller of invoke; if the value has a primitive type, it is first appropriately wrapped in an object. If the underlying method return type is void, the invocation returns null.

Parameters:

obj - the object the underlying method is invoked from

args - the arguments used for the method call

Returns:

the result of dispatching the method represented by this object on obj with parameters args

Throws:

IllegalAccessException - if this Method object enforces Java language access control and the underlying method is inaccessible.

IllegalArgumentException - if the method is an instance method and the specified object argument is not an instance of the class or interface declaring the underlying method (or of a subclass or implementor thereof); if the number of actual and formal parameters differ; if an unwrapping conversion for primitive arguments fails; or if, after possible unwrapping, a parameter value cannot be converted to the corresponding formal parameter type by a method invocation conversion.

InvocationTargetException - if the underlying method throws an exception.

NullPointerException - if the specified object is null and the method is an instance method.

ExceptionInInitializerError - if the initialization provoked by this method fails.