| /******************************************************************************* |
| * Copyright (c) 2009 Oracle. All rights reserved. |
| * This program and the accompanying materials are made available under the |
| * terms of the Eclipse Public License v1.0, which accompanies this distribution |
| * and is available at http://www.eclipse.org/legal/epl-v10.html. |
| * |
| * Contributors: |
| * Oracle - initial API and implementation |
| ******************************************************************************/ |
| package org.eclipse.jpt.utility.internal; |
| |
| import java.io.Serializable; |
| |
| /** |
| * Provide a container for passing an object that can be changed by the recipient. |
| * |
| * @see SynchronizedObject |
| */ |
| public class ObjectReference<V> |
| implements Cloneable, Serializable |
| { |
| /** Backing value. */ |
| private volatile V value; |
| |
| private static final long serialVersionUID = 1L; |
| |
| |
| // ********** constructors ********** |
| |
| /** |
| * Create an object reference with the specified initial value. |
| */ |
| public ObjectReference(V value) { |
| super(); |
| this.value = value; |
| } |
| |
| /** |
| * Create an object reference with an initial value of |
| * <code>null</code>. |
| */ |
| public ObjectReference() { |
| this(null); |
| } |
| |
| |
| // ********** accessors ********** |
| |
| /** |
| * Return the current value. |
| */ |
| public V getValue() { |
| return this.value; |
| } |
| |
| /** |
| * Return whether the current value is equal to the specified value. |
| */ |
| public boolean valueEquals(V v) { |
| return Tools.valuesAreEqual(this.value, v); |
| } |
| |
| /** |
| * Return whether the current value is not equal to the specified value. |
| */ |
| public boolean valueNotEqual(V v) { |
| return Tools.valuesAreDifferent(this.value, v); |
| } |
| |
| /** |
| * Return whether the current value is <code>null</code>. |
| */ |
| public boolean isNull() { |
| return this.value == null; |
| } |
| |
| /** |
| * Return whether the current value is not <code>null</code>. |
| */ |
| public boolean isNotNull() { |
| return this.value != null; |
| } |
| |
| /** |
| * Set the value. |
| * Return the previous value. |
| */ |
| public V setValue(V value) { |
| V old = this.value; |
| this.value = value; |
| return old; |
| } |
| |
| /** |
| * Set the value to <code>null</code>. |
| * Return the previous value. |
| */ |
| public V setNull() { |
| return this.setValue(null); |
| } |
| |
| |
| // ********** standard methods ********** |
| |
| @Override |
| public ObjectReference<V> clone() { |
| try { |
| @SuppressWarnings("unchecked") |
| ObjectReference<V> clone = (ObjectReference<V>) super.clone(); |
| return clone; |
| } catch (CloneNotSupportedException ex) { |
| throw new InternalError(); |
| } |
| } |
| |
| @Override |
| public boolean equals(Object obj) { |
| return (obj instanceof ObjectReference<?>) && |
| Tools.valuesAreEqual(this.value, ((ObjectReference<?>) obj).value); |
| } |
| |
| @Override |
| public int hashCode() { |
| return (this.value == null) ? 0 : this.value.hashCode(); |
| } |
| |
| @Override |
| public String toString() { |
| return '[' + String.valueOf(this.value) + ']'; |
| } |
| |
| } |