Coverage Summary for Class: AbstractIndexedListIterator (com.google.common.collect)

1 /*
2  * Copyright (C) 2009 The Guava Authors
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  * http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 package com.google.common.collect;
18 
19 import static com.google.common.base.Preconditions.checkPositionIndex;
20 
21 import com.google.common.annotations.GwtCompatible;
22 import java.util.ListIterator;
23 import java.util.NoSuchElementException;
24 
25 /**
26  * This class provides a skeletal implementation of the {@link ListIterator} interface across a
27  * fixed number of elements that may be retrieved by position. It does not support {@link #remove},
28  * {@link #set}, or {@link #add}.
29  *
30  * @author Jared Levy
31  */
32 @GwtCompatible
33 abstract class AbstractIndexedListIterator<E> extends UnmodifiableListIterator<E> {
34   private final int size;
35   private int position;
36 
37   /** Returns the element with the specified index. This method is called by {@link #next()}. */
38   protected abstract E get(int index);
39 
40   /**
41    * Constructs an iterator across a sequence of the given size whose initial position is 0. That
42    * is, the first call to {@link #next()} will return the first element (or throw {@link
43    * NoSuchElementException} if {@code size} is zero).
44    *
45    * @throws IllegalArgumentException if {@code size} is negative
46    */
47   protected AbstractIndexedListIterator(int size) {
48     this(size, 0);
49   }
50 
51   /**
52    * Constructs an iterator across a sequence of the given size with the given initial position.
53    * That is, the first call to {@link #nextIndex()} will return {@code position}, and the first
54    * call to {@link #next()} will return the element at that index, if available. Calls to {@link
55    * #previous()} can retrieve the preceding {@code position} elements.
56    *
57    * @throws IndexOutOfBoundsException if {@code position} is negative or is greater than {@code
58    *     size}
59    * @throws IllegalArgumentException if {@code size} is negative
60    */
61   protected AbstractIndexedListIterator(int size, int position) {
62     checkPositionIndex(position, size);
63     this.size = size;
64     this.position = position;
65   }
66 
67   @Override
68   public final boolean hasNext() {
69     return position < size;
70   }
71 
72   @Override
73   public final E next() {
74     if (!hasNext()) {
75       throw new NoSuchElementException();
76     }
77     return get(position++);
78   }
79 
80   @Override
81   public final int nextIndex() {
82     return position;
83   }
84 
85   @Override
86   public final boolean hasPrevious() {
87     return position > 0;
88   }
89 
90   @Override
91   public final E previous() {
92     if (!hasPrevious()) {
93       throw new NoSuchElementException();
94     }
95     return get(--position);
96   }
97 
98   @Override
99   public final int previousIndex() {
100     return position - 1;
101   }
102 }