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| 1 /* | |
| 2 * Copyright (C) 2012 René Jeschke <rene_jeschke@yahoo.de> | |
| 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 package com.github.rjeschke.neetutils.dispose; | |
| 17 | |
| 18 /** | |
| 19 * Specialized linked list to hold weak references or similar stuff. Adding and | |
| 20 * removing is guaranteed O(1). | |
| 21 * | |
| 22 * @author René Jeschke <rene_jeschke@yhoo.de> | |
| 23 */ | |
| 24 public class ReferenceList<T> | |
| 25 { | |
| 26 private Node<T> root; | |
| 27 private int size; | |
| 28 | |
| 29 /** | |
| 30 * Constructor. | |
| 31 */ | |
| 32 public ReferenceList() | |
| 33 { | |
| 34 // empty | |
| 35 } | |
| 36 | |
| 37 /** | |
| 38 * Gets the number of items currently in this list. | |
| 39 * | |
| 40 * @return The size. | |
| 41 */ | |
| 42 public int size() | |
| 43 { | |
| 44 return this.size; | |
| 45 } | |
| 46 | |
| 47 /** | |
| 48 * Checks if this list is empty. | |
| 49 * | |
| 50 * @return <code>true</code> is this list is empty | |
| 51 */ | |
| 52 public boolean isEmpty() | |
| 53 { | |
| 54 return this.size == 0; | |
| 55 } | |
| 56 | |
| 57 /** | |
| 58 * Adds a value to this list (at head). | |
| 59 * | |
| 60 * @param value | |
| 61 * Value to add | |
| 62 * @return Node reference needed for remove | |
| 63 */ | |
| 64 public Node<T> add(final T value) | |
| 65 { | |
| 66 final Node<T> node = new Node<T>(value); | |
| 67 this.size++; | |
| 68 if (this.root != null) | |
| 69 { | |
| 70 node.next = this.root; | |
| 71 this.root.previous = node; | |
| 72 } | |
| 73 this.root = node; | |
| 74 | |
| 75 return node; | |
| 76 } | |
| 77 | |
| 78 /** | |
| 79 * Removes the last added Node. | |
| 80 * | |
| 81 * @return The last added Node or <code>null</code> if this list is empty. | |
| 82 */ | |
| 83 public Node<T> removeLast() | |
| 84 { | |
| 85 if (this.root == null) | |
| 86 { | |
| 87 return null; | |
| 88 } | |
| 89 | |
| 90 this.size--; | |
| 91 final Node<T> node = this.root; | |
| 92 if (node.next != null) | |
| 93 { | |
| 94 node.next.previous = null; | |
| 95 } | |
| 96 this.root = node.next; | |
| 97 | |
| 98 node.next = node.previous = null; | |
| 99 node.inside = false; | |
| 100 return node; | |
| 101 } | |
| 102 | |
| 103 /** | |
| 104 * Removes the given Node from this list. Multiple removes are prevented. | |
| 105 * | |
| 106 * @param node | |
| 107 * The Node to remove | |
| 108 */ | |
| 109 public void remove(final Node<T> node) | |
| 110 { | |
| 111 if (!node.inside) | |
| 112 { | |
| 113 return; | |
| 114 } | |
| 115 | |
| 116 this.size--; | |
| 117 if (node.previous == null) | |
| 118 { | |
| 119 this.root = node.next; | |
| 120 } | |
| 121 else | |
| 122 { | |
| 123 node.previous.next = node.next; | |
| 124 if (node.next != null) | |
| 125 { | |
| 126 node.next.previous = node.previous; | |
| 127 } | |
| 128 } | |
| 129 | |
| 130 node.next = node.previous = null; | |
| 131 node.inside = false; | |
| 132 } | |
| 133 | |
| 134 /** | |
| 135 * | |
| 136 * | |
| 137 * @author René Jeschke <rene_jeschke@yhoo.de> | |
| 138 */ | |
| 139 public static class Node<T> | |
| 140 { | |
| 141 final T value; | |
| 142 boolean inside = true; | |
| 143 Node<T> previous; | |
| 144 Node<T> next; | |
| 145 | |
| 146 public Node(final T value) | |
| 147 { | |
| 148 this.value = value; | |
| 149 } | |
| 150 | |
| 151 public T value() | |
| 152 { | |
| 153 return this.value; | |
| 154 } | |
| 155 | |
| 156 @Override | |
| 157 public String toString() | |
| 158 { | |
| 159 return "Node: " + this.value; | |
| 160 } | |
| 161 } | |
| 162 } | |
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