org.apache.commons.lang
Class ObjectUtils.Null

java.lang.Object
  |
  +--org.apache.commons.lang.ObjectUtils.Null

All Implemented Interfaces:

Serializable

Enclosing class:

ObjectUtils

public static class ObjectUtils.Null

extends Object

implements Serializable

Class used as a null placeholder where null has another meaning.

For example, in a HashMap the get(key) method returns null if the Map contains null or if there is no matching key. The Null placeholder can be used to distinguish between these two cases.

Another example is HashTable, where null cannot be stored.

See Also:

Serialized Form

Constructor Summary

private

ObjectUtils.Null() Restricted constructor - singleton

Method Summary

private Object

readResolve() Ensure singleton.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

ObjectUtils.Null

private ObjectUtils.Null()

Restricted constructor - singleton

Method Detail

readResolve

private Object readResolve()

Ensure singleton.

Returns:

the singleton value