org.codehaus.groovy.runtime
Class NullObject

java.lang.Object
  groovy.lang.GroovyObjectSupport
      org.codehaus.groovy.runtime.NullObject

All Implemented Interfaces:

GroovyObject

public class NullObject
extends GroovyObjectSupport

Method Summary

boolean	asBoolean() A null object always coerces to false.
java.lang.Object	asType(java.lang.Class c) Type conversion method for null.
java.lang.Object	clone() Since this is implemented as a singleton, we should avoid the use of the clone method
boolean	equals(java.lang.Object to) null is only equal to null
static NullObject	getNullObject() get the NullObject reference
java.lang.Object	getProperty(java.lang.String property) Tries to get a property on null, which will always fail
int	hashCode()
java.lang.Object	invokeMethod(java.lang.String name, java.lang.Object args) Tries to invoke a method on null, which will always fail
boolean	is(java.lang.Object other) The method "is" is used to test for equal references.
java.util.Iterator	iterator() iterator() method to be able to iterate on null.
java.lang.Object	plus(java.lang.Object o) Fallback for null+null.
java.lang.Object	plus(java.lang.String s) Allows to add a String to null.
void	setProperty(java.lang.String property, java.lang.Object newValue) Tries to set a property on null, which will always fail
java.lang.String	toString()

Methods inherited from class groovy.lang.GroovyObjectSupport

getMetaClass, setMetaClass

Methods inherited from class java.lang.Object

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

Method Detail

getNullObject

public static NullObject getNullObject()

get the NullObject reference

Returns:

the null object

clone

public java.lang.Object clone()

Since this is implemented as a singleton, we should avoid the use of the clone method

Overrides:

clone in class java.lang.Object

getProperty

public java.lang.Object getProperty(java.lang.String property)

Tries to get a property on null, which will always fail

Specified by:

getProperty in interface GroovyObject

Overrides:

getProperty in class GroovyObjectSupport

Parameters:

property - - the property to get

Returns:

a NPE

setProperty

public void setProperty(java.lang.String property,
                        java.lang.Object newValue)

Tries to set a property on null, which will always fail

Specified by:

setProperty in interface GroovyObject

Overrides:

setProperty in class GroovyObjectSupport

Parameters:

property - - the proprty to set

newValue - - the new value of the property

invokeMethod

public java.lang.Object invokeMethod(java.lang.String name,
                                     java.lang.Object args)

Tries to invoke a method on null, which will always fail

Specified by:

invokeMethod in interface GroovyObject

Overrides:

invokeMethod in class GroovyObjectSupport

Parameters:

name - the name of the method to invoke

args - - arguments to the method

Returns:

a NPE

equals

public boolean equals(java.lang.Object to)

null is only equal to null

Overrides:

equals in class java.lang.Object

Parameters:

to - - the reference object with which to compare

Returns:

- true if this object is the same as the to argument

iterator

public java.util.Iterator iterator()

iterator() method to be able to iterate on null. Note: this part is from Invoker

Returns:

an iterator for an empty list

plus

public java.lang.Object plus(java.lang.String s)

Allows to add a String to null. The result is concatenated String of the result of calling toString() on this object and the String in the parameter.

Parameters:

s - - the String to concatenate

Returns:

the concatenated string

plus

public java.lang.Object plus(java.lang.Object o)

Fallback for null+null. The result is always a NPE. The plus(String) version will catch the case of adding a non null String to null.

Parameters:

o - - the Object

Returns:

nothing

is

public boolean is(java.lang.Object other)

The method "is" is used to test for equal references. This method will return true only if the given parameter is null

Parameters:

other - - the object to test

Returns:

true if other is null

asType

public java.lang.Object asType(java.lang.Class c)

Type conversion method for null.

Parameters:

c - - the class to convert to

Returns:

always null

asBoolean

public boolean asBoolean()

A null object always coerces to false.

Returns:

false

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

hashCode

public int hashCode()

Overrides:

hashCode in class java.lang.Object