/*
* 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.checkPositionIndex;
import com.google.common.annotations.GwtCompatible;
import java.util.ListIterator;
import java.util.NoSuchElementException;
/**
* This class provides a skeletal implementation of the {@link ListIterator}
* interface across a fixed number of elements that may be retrieved by
* position. It does not support {@link #remove}, {@link #set}, or {@link #add}.
*
* @author Jared Levy
*/
@GwtCompatible
abstract class AbstractIndexedListIterator<E>
extends UnmodifiableListIterator<E> {
private final int size;
private int position;
/**
* Returns the element with the specified index. This method is called by
* {@link #next()}.
*/
protected abstract E get(int index);
/**
* Constructs an iterator across a sequence of the given size whose initial
* position is 0. That is, the first call to {@link #next()} will return the
* first element (or throw {@link NoSuchElementException} if {@code size} is
* zero).
*
* @throws IllegalArgumentException if {@code size} is negative
*/
protected AbstractIndexedListIterator(int size) {
this(size, 0);
}
/**
* Constructs an iterator across a sequence of the given size with the given
* initial position. That is, the first call to {@link #nextIndex()} will
* return {@code position}, and the first call to {@link #next()} will return
* the element at that index, if available. Calls to {@link #previous()} can
* retrieve the preceding {@code position} elements.
*
* @throws IndexOutOfBoundsException if {@code position} is negative or is
* greater than {@code size}
* @throws IllegalArgumentException if {@code size} is negative
*/
protected AbstractIndexedListIterator(int size, int position) {
checkPositionIndex(position, size);
this.size = size;
this.position = position;
}
@Override
public final boolean hasNext() {
return position < size;
}
@Override
public final E next() {
if (!hasNext()) {
throw new NoSuchElementException();
}
return get(position++);
}
@Override
public final int nextIndex() {
return position;
}
@Override
public final boolean hasPrevious() {
return position > 0;
}
@Override
public final E previous() {
if (!hasPrevious()) {
throw new NoSuchElementException();
}
return get(--position);
}
@Override
public final int previousIndex() {
return position - 1;
}
}
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