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Java example source code file (ForwardingObject.java)
The ForwardingObject.java Java example source code/* * Copyright (C) 2007 The Guava Authors * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package com.google.common.collect; import com.google.common.annotations.GwtCompatible; import java.io.Serializable; /** * An abstract base class for implementing the <a * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>. * The {@link #delegate()} method must be overridden to return the instance * being decorated. * * <p>This class does not forward the {@code hashCode} and {@code equals} * methods through to the backing object, but relies on {@code Object}'s * implementation. This is necessary to preserve the symmetry of {@code equals}. * Custom definitions of equality are usually based on an interface, such as * {@code Set} or {@code List}, so that the implementation of {@code equals} can * cast the object being tested for equality to the custom interface. {@code * ForwardingObject} implements no such custom interfaces directly; they * are implemented only in subclasses. Therefore, forwarding {@code equals} * would break symmetry, as the forwarding object might consider itself equal to * the object being tested, but the reverse could not be true. This behavior is * consistent with the JDK's collection wrappers, such as * {@link java.util.Collections#unmodifiableCollection}. Use an * interface-specific subclass of {@code ForwardingObject}, such as {@link * ForwardingList}, to preserve equality behavior, or override {@code equals} * directly. * * <p>The {@code toString} method is forwarded to the delegate. Although this * class does not implement {@link Serializable}, a serializable subclass may be * created since this class has a parameter-less constructor. * * @author Mike Bostock * @since 2.0 */ @GwtCompatible public abstract class ForwardingObject { /** Constructor for use by subclasses. */ protected ForwardingObject() {} /** * Returns the backing delegate instance that methods are forwarded to. * Abstract subclasses generally override this method with an abstract method * that has a more specific return type, such as {@link * ForwardingSet#delegate}. Concrete subclasses override this method to supply * the instance being decorated. */ protected abstract Object delegate(); /** * Returns the string representation generated by the delegate's * {@code toString} method. */ @Override public String toString() { return delegate().toString(); } /* No equals or hashCode. See class comments for details. */ } Other Java examples (source code examples)Here is a short list of links related to this Java ForwardingObject.java source code file: |
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