/*
 * 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 ListIterator interface across a fixed number of elements that may be retrieved by position. It does not support UnmodifiableIterator.remove, UnmodifiableListIterator.set, or UnmodifiableListIterator.add. 
Author:
Jared Levy/**
 * 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 next(). /** 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 next() will return the first element (or throw NoSuchElementException if size is zero). 
Throws:
IllegalArgumentException – if size is negative/**
   * 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 nextIndex() will return position, and the first call to next() will return the element at that index, if available. Calls to previous() can retrieve the preceding position elements. 
Throws:
IndexOutOfBoundsException – if position is negative or is greater than 
    size
IllegalArgumentException – if size is negative/**
   * 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;
  }
}