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/*
* 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.Beta;
import com.google.common.annotations.GwtCompatible;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.ListIterator;
import javax.annotation.Nullable;
/**
* A list which forwards all its method calls to another list. Subclasses should
* override one or more methods to modify the behavior of the backing list as
* desired per the decorator pattern.
*
* This class does not implement {@link java.util.RandomAccess}. If the
* delegate supports random access, the {@code ForwardingList} subclass should
* implement the {@code RandomAccess} interface.
*
*
Warning: The methods of {@code ForwardingList} forward
* indiscriminately to the methods of the delegate. For example,
* overriding {@link #add} alone will not change the behavior of {@link
* #addAll}, which can lead to unexpected behavior. In this case, you should
* override {@code addAll} as well, either providing your own implementation, or
* delegating to the provided {@code standardAddAll} method.
*
*
{@code default} method warning: This class does not forward calls to {@code
* default} methods. Instead, it inherits their default implementations. When those implementations
* invoke methods, they invoke methods on the {@code ForwardingList}.
*
*
The {@code standard} methods and any collection views they return are not
* guaranteed to be thread-safe, even when all of the methods that they depend
* on are thread-safe.
*
* @author Mike Bostock
* @author Louis Wasserman
* @since 2.0
*/
@GwtCompatible
public abstract class ForwardingList extends ForwardingCollection implements List {
// TODO(lowasser): identify places where thread safety is actually lost
/** Constructor for use by subclasses. */
protected ForwardingList() {}
@Override
protected abstract List delegate();
@Override
public void add(int index, E element) {
delegate().add(index, element);
}
@CanIgnoreReturnValue
@Override
public boolean addAll(int index, Collection elements) {
return delegate().addAll(index, elements);
}
@Override
public E get(int index) {
return delegate().get(index);
}
@Override
public int indexOf(Object element) {
return delegate().indexOf(element);
}
@Override
public int lastIndexOf(Object element) {
return delegate().lastIndexOf(element);
}
@Override
public ListIterator listIterator() {
return delegate().listIterator();
}
@Override
public ListIterator listIterator(int index) {
return delegate().listIterator(index);
}
@CanIgnoreReturnValue
@Override
public E remove(int index) {
return delegate().remove(index);
}
@CanIgnoreReturnValue
@Override
public E set(int index, E element) {
return delegate().set(index, element);
}
@Override
public List subList(int fromIndex, int toIndex) {
return delegate().subList(fromIndex, toIndex);
}
@Override
public boolean equals(@Nullable Object object) {
return object == this || delegate().equals(object);
}
@Override
public int hashCode() {
return delegate().hashCode();
}
/**
* A sensible default implementation of {@link #add(Object)}, in terms of
* {@link #add(int, Object)}. If you override {@link #add(int, Object)}, you
* may wish to override {@link #add(Object)} to forward to this
* implementation.
*
* @since 7.0
*/
protected boolean standardAdd(E element) {
add(size(), element);
return true;
}
/**
* A sensible default implementation of {@link #addAll(int, Collection)}, in
* terms of the {@code add} method of {@link #listIterator(int)}. If you
* override {@link #listIterator(int)}, you may wish to override {@link
* #addAll(int, Collection)} to forward to this implementation.
*
* @since 7.0
*/
protected boolean standardAddAll(int index, Iterable elements) {
return Lists.addAllImpl(this, index, elements);
}
/**
* A sensible default implementation of {@link #indexOf}, in terms of {@link
* #listIterator()}. If you override {@link #listIterator()}, you may wish to
* override {@link #indexOf} to forward to this implementation.
*
* @since 7.0
*/
protected int standardIndexOf(@Nullable Object element) {
return Lists.indexOfImpl(this, element);
}
/**
* A sensible default implementation of {@link #lastIndexOf}, in terms of
* {@link #listIterator(int)}. If you override {@link #listIterator(int)}, you
* may wish to override {@link #lastIndexOf} to forward to this
* implementation.
*
* @since 7.0
*/
protected int standardLastIndexOf(@Nullable Object element) {
return Lists.lastIndexOfImpl(this, element);
}
/**
* A sensible default implementation of {@link #iterator}, in terms of
* {@link #listIterator()}. If you override {@link #listIterator()}, you may
* wish to override {@link #iterator} to forward to this implementation.
*
* @since 7.0
*/
protected Iterator standardIterator() {
return listIterator();
}
/**
* A sensible default implementation of {@link #listIterator()}, in terms of
* {@link #listIterator(int)}. If you override {@link #listIterator(int)}, you
* may wish to override {@link #listIterator()} to forward to this
* implementation.
*
* @since 7.0
*/
protected ListIterator standardListIterator() {
return listIterator(0);
}
/**
* A sensible default implementation of {@link #listIterator(int)}, in terms
* of {@link #size}, {@link #get(int)}, {@link #set(int, Object)}, {@link
* #add(int, Object)}, and {@link #remove(int)}. If you override any of these
* methods, you may wish to override {@link #listIterator(int)} to forward to
* this implementation.
*
* @since 7.0
*/
@Beta
protected ListIterator standardListIterator(int start) {
return Lists.listIteratorImpl(this, start);
}
/**
* A sensible default implementation of {@link #subList(int, int)}. If you
* override any other methods, you may wish to override {@link #subList(int,
* int)} to forward to this implementation.
*
* @since 7.0
*/
@Beta
protected List standardSubList(int fromIndex, int toIndex) {
return Lists.subListImpl(this, fromIndex, toIndex);
}
/**
* A sensible definition of {@link #equals(Object)} in terms of {@link #size}
* and {@link #iterator}. If you override either of those methods, you may
* wish to override {@link #equals(Object)} to forward to this implementation.
*
* @since 7.0
*/
@Beta
protected boolean standardEquals(@Nullable Object object) {
return Lists.equalsImpl(this, object);
}
/**
* A sensible definition of {@link #hashCode} in terms of {@link #iterator}.
* If you override {@link #iterator}, you may wish to override {@link
* #hashCode} to forward to this implementation.
*
* @since 7.0
*/
@Beta
protected int standardHashCode() {
return Lists.hashCodeImpl(this);
}
}