org.jboss.util.Null Maven / Gradle / Ivy
/*
* JBoss, Home of Professional Open Source
* Copyright 2005, JBoss Inc., and individual contributors as indicated
* by the @authors tag. See the copyright.txt in the distribution for a
* full listing of individual contributors.
*
* This is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation; either version 2.1 of
* the License, or (at your option) any later version.
*
* This software is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this software; if not, write to the Free
* Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
* 02110-1301 USA, or see the FSF site: http://www.fsf.org.
*/
package org.jboss.util;
import java.io.Serializable;
/**
* A class that represents null.
*
* {@link Null#VALUE} is used to given an object variable a dual-mode
* nullified value, where null would indicate that the value is
* empty, and {@link Null#VALUE} would idicate that the value has been
* set to null (or something to that effect).
*
* @version $Revision: 2800 $
* @author Jason Dillon
*/
public final class Null
implements Serializable
{
/** The serialVersionUID */
private static final long serialVersionUID = -403173436435490144L;
/** The primary instance of Null. */
public static final Null VALUE = new Null();
/** Do not allow public construction. */
private Null() {}
/**
* Return a string representation.
*
* @return Null
*/
public String toString() {
return null;
}
/**
* Returns zero.
*
* @return Zero.
*/
public int hashCode() {
return 0;
}
/**
* Check if the given object is a Null instance or null.
*
* @param obj Object to test.
* @return True if the given object is a Null instance or null.
*/
public boolean equals(final Object obj) {
if (obj == this) return true;
return (obj == null || obj.getClass() == getClass());
}
}