[Chapter 13] Method

#

| Chapter 13 The java.lang.reflect Package |

# Method

## Name

Method

## Synopsis

Class Name:

  `java.lang.reflect.Method`

Superclass:

  `java.lang.Object`

Immediate Subclasses:

  None

Interfaces Implemented:

  `java.lang.reflect.Member`

Availability:

  New as of JDK 1.1

## Description

The `Method` class represents a method of a class. A `Method` object can be obtained by calling the `getMethod()` method of a `Class` object. `Method` provides methods for getting the name, modifiers, return type, parameters, exceptions, and declaring class of a method. The `invoke()` method can be used to run the method.

## Class Summary

    public final class java.lang.reflect.Method extends java.lang.Object
                       implements java.lang.reflect.Member {
      // Instance Methods
      public boolean equals(Object obj);
      public Class getDeclaringClass();
      public Class[] getExceptionTypes();
      public native int getModifiers();
      public String getName();
      public Class[] getParameterTypes();
      public Class getReturnType();
      public int hashCode();
      public native Object invoke(Object obj, Object[] args);
      public String toString();
    }

## Instance Methods

### equals

#### public boolean equals(Object obj)

Parameters

  `obj`

    The object to be compared with this object.

Returns

  `true` if the objects are equal; `false` if they are not.

Overrides

  `Object.equals()`

Description

  This method returns `true` if `obj` is an instance of `Method`, and it is equivalent to this `Method`.

### getDeclaringClass

#### public Class getDeclaringClass()

Returns

  The `Class` object that represents the class that declared this method.

Implements

  `Member.getDeclaringClass()`

Description

  This method returns the `Class` object for the class in which this method is declared.

### getExceptionTypes

#### public Class[] getExceptionTypes()

Returns

  An array that contains the `Class` objects that describe the exceptions that can be thrown by this method.

Description

  This method returns an array of `Class` objects that represents the `throws` clause of this method. If the method does not throw any exceptions, an array of length 0 is returned. As of Java 1.1.2, this method is not properly supported: it always returns an empty array.

### getModifiers

#### public native int getModifiers()

Returns

  An integer that represents the modifier keywords used to declare this method.

Implements

  `Member.getModifiers()`

Description

  This method returns an integer value that represents the modifiers of this method. The `Modifier` class should be used to decode the returned value.

### getName

#### public String getName()

Returns

  The name of this method as a `String`.

Implements

  `Member.getName()`

Description

  This method returns the name of this method.

### getParameterTypes

#### public Class[] getParameterTypes()

Returns

  An array that contains the `Class` objects that describe the parameter types that this method accepts.

Description

  This method returns an array of `Class` objects that represents the parameter types this method accepts. The parameter types are listed in the order in which they are declared. If the method does not take any parameters, an array of length 0 is returned.

### getReturnType

#### public Class getReturnType()

Returns

  The `Class` object that represents the return type of this method.

Description

  This method returns the `Class` object for the type that this method returns.

### hashCode

#### public int hashCode()

Returns

  A hashcode for this object.

Overrides

  `Object.hashCode()`

Description

  This method returns a hashcode for this `Method`.

### invoke

####

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

Parameters

  `obj`

    The instance upon which this method is invoked.

  `args`

    An array of arguments to be passed to this method.

Returns

  A `Object` that contains the return value of the invoked method.

Throws

  `IllegalAccessException`

    If the method is inaccessible.

  `IllegalArgumentException`

    If `obj` is not the correct type, or if `args` is the wrong length or contains the wrong types.

  `InvocationTargetException`

    If the method itself throws an exception.

  `NullPointerException`

    If `obj` is `null`.

Description

  This method executes the method represented by this object on the given object using the given array of arguments. If the method is declared `static`, the `obj` parameter is ignored. Otherwise, the object supplied must be an instance of the class that declares this method.

  If a particular parameter is of a primitive type, the corresponding argument is automatically unwrapped and converted to the appropriate type, if possible. If that is not possible, an `IllegalArgumentException` is thrown. If the method itself throws an exception, the exception is placed in an `InvocationTargetException`, which is then thrown to the caller of `invoke()`.

  If the method completes normally, the value it returns is returned. If the value is of a primitive type, the value is wrapped in an appropriate object and the object is returned. If the return type is `void`, `null` is returned.

### toString

#### public String toString()

Returns

  A string representation of this object.

Overrides

  `Object.toString()`

Description

  This method returns a string representation of this `Method`. This string contains the access modifiers of the method, if any, followed by the return type, the fully qualified name of the declaring class, a period, the name of the method, and a list of the parameters of the method, if any. The list is enclosed by parentheses and the individual parameters are separated by commas. If the method does not have any parameters, just the parentheses are included in the string.

## Inherited Methods

Method | Inherited From | Method | Inherited From
--- | --- | --- | ---
`clone()` | `Object` | `finalize()` | `Object`
`getClass()` | `Object` | `notify()` | `Object`
`notifyAll()` | `Object` | `wait()` | `Object`
`wait(long)` | `Object` | `wait(long, int)` | `Object`

## See Also

`Class`, `Constructor`, `Field`, `IllegalAccessException`, `IllegalArgumentException`, `InvocationTargetException`, `Member`, `Modifier`, `NullPointerException`, `Object`

Member |  | Modifier