001/* 002 * Copyright (C) 2007 The Guava Authors 003 * 004 * Licensed under the Apache License, Version 2.0 (the "License"); 005 * you may not use this file except in compliance with the License. 006 * You may obtain a copy of the License at 007 * 008 * http://www.apache.org/licenses/LICENSE-2.0 009 * 010 * Unless required by applicable law or agreed to in writing, software 011 * distributed under the License is distributed on an "AS IS" BASIS, 012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 013 * See the License for the specific language governing permissions and 014 * limitations under the License. 015 */ 016 017package com.google.common.collect; 018 019import com.google.common.annotations.GwtCompatible; 020import com.google.errorprone.annotations.CanIgnoreReturnValue; 021import java.util.ListIterator; 022 023/** 024 * A list iterator which forwards all its method calls to another list iterator. Subclasses should 025 * override one or more methods to modify the behavior of the backing iterator as desired per the <a 026 * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>. 027 * 028 * <p><b>{@code default} method warning:</b> This class forwards calls to <i>only some</i> {@code 029 * default} methods. Specifically, it forwards calls only for methods that existed <a 030 * href="https://docs.oracle.com/javase/7/docs/api/java/util/ListIterator.html">before {@code 031 * default} methods were introduced</a>. For newer methods, like {@code forEachRemaining}, it 032 * inherits their default implementations. When those implementations invoke methods, they invoke 033 * methods on the {@code ForwardingListIterator}. 034 * 035 * @author Mike Bostock 036 * @since 2.0 037 */ 038@GwtCompatible 039public abstract class ForwardingListIterator<E> extends ForwardingIterator<E> 040 implements ListIterator<E> { 041 042 /** Constructor for use by subclasses. */ 043 protected ForwardingListIterator() {} 044 045 @Override 046 protected abstract ListIterator<E> delegate(); 047 048 @Override 049 public void add(E element) { 050 delegate().add(element); 051 } 052 053 @Override 054 public boolean hasPrevious() { 055 return delegate().hasPrevious(); 056 } 057 058 @Override 059 public int nextIndex() { 060 return delegate().nextIndex(); 061 } 062 063 @CanIgnoreReturnValue 064 @Override 065 public E previous() { 066 return delegate().previous(); 067 } 068 069 @Override 070 public int previousIndex() { 071 return delegate().previousIndex(); 072 } 073 074 @Override 075 public void set(E element) { 076 delegate().set(element); 077 } 078}