/*
* 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 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 <a
* href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
*
* <p>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.
*
* <p><b>Warning:</b> The methods of {@code ForwardingList} forward
* <b>indiscriminately</b> to the methods of the delegate. For example,
* overriding {@link #add} alone <b>will not</b> 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.
*
* <p>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 (imported from Google Collections Library)
*/
@
GwtCompatible
public abstract class
ForwardingList<E> extends
ForwardingCollection<E>
implements
List<E> {
// TODO(user): identify places where thread safety is actually lost
/** Constructor for use by subclasses. */
protected
ForwardingList() {}
@
Override protected abstract
List<E>
delegate();
@
Override
public void
add(int
index, E
element) {
delegate().
add(
index,
element);
}
@
Override
public boolean
addAll(int
index,
Collection<? extends E>
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<E>
listIterator() {
return
delegate().
listIterator();
}
@
Override
public
ListIterator<E>
listIterator(int
index) {
return
delegate().
listIterator(
index);
}
@
Override
public E
remove(int
index) {
return
delegate().
remove(
index);
}
@
Override
public E
set(int
index, E
element) {
return
delegate().
set(
index,
element);
}
@
Override
public
List<E>
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<? extends E>
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<E>
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<E>
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<E>
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<E>
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);
}
}