/*
* Copyright (C) 2009 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 static com.google.common.base.
Preconditions.checkNotNull;
import com.google.common.annotations.
GwtCompatible;
import com.google.common.base.
Preconditions;
import java.util.
List;
import javax.annotation.
Nullable;
/**
* Implementation of {@link ImmutableList} with exactly one element.
*
* @author Hayward Chan
*/
@
GwtCompatible(serializable = true, emulated = true)
@
SuppressWarnings("serial") // uses writeReplace(), not default serialization
final class
SingletonImmutableList<E> extends
ImmutableList<E> {
final transient E
element;
SingletonImmutableList(E
element) {
this.
element =
checkNotNull(
element);
}
@
Override
public E
get(int
index) {
Preconditions.
checkElementIndex(
index, 1);
return
element;
}
@
Override public int
indexOf(@
Nullable Object object) {
return
element.
equals(
object) ? 0 : -1;
}
@
Override public
UnmodifiableIterator<E>
iterator() {
return
Iterators.
singletonIterator(
element);
}
@
Override public int
lastIndexOf(@
Nullable Object object) {
return
indexOf(
object);
}
@
Override
public int
size() {
return 1;
}
@
Override public
ImmutableList<E>
subList(int
fromIndex, int
toIndex) {
Preconditions.
checkPositionIndexes(
fromIndex,
toIndex, 1);
return (
fromIndex ==
toIndex) ?
ImmutableList.<E>
of() : this;
}
@
Override public
ImmutableList<E>
reverse() {
return this;
}
@
Override public boolean
contains(@
Nullable Object object) {
return
element.
equals(
object);
}
@
Override public boolean
equals(@
Nullable Object object) {
if (
object == this) {
return true;
}
if (
object instanceof
List) {
List<?>
that = (
List<?>)
object;
return
that.
size() == 1 &&
element.
equals(
that.
get(0));
}
return false;
}
@
Override public int
hashCode() {
// not caching hash code since it could change if the element is mutable
// in a way that modifies its hash code.
return 31 +
element.
hashCode();
}
@
Override public
String toString() {
String elementToString =
element.
toString();
return new
StringBuilder(
elementToString.
length() + 2)
.
append('[')
.
append(
elementToString)
.
append(']')
.
toString();
}
@
Override public boolean
isEmpty() {
return false;
}
@
Override boolean
isPartialView() {
return false;
}
@
Override
int
copyIntoArray(
Object[]
dst, int
offset) {
dst[
offset] =
element;
return
offset + 1;
}
}