01 /*
02 * Java Genetic Algorithm Library (jenetics-3.5.0).
03 * Copyright (c) 2007-2016 Franz Wilhelmstötter
04 *
05 * Licensed under the Apache License, Version 2.0 (the "License");
06 * you may not use this file except in compliance with the License.
07 * You may obtain a copy of the License at
08 *
09 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 *
17 * Author:
18 * Franz Wilhelmstötter (franz.wilhelmstoetter@gmx.at)
19 */
20 package org.jenetics.internal.collection;
21
22 import java.util.function.Consumer;
23
24 /**
25 * Minimal implementation of stack data-structure. {@code Null} values are not
26 * permitted, but not checked.
27 *
28 * <pre>{@code
29 * final Stack<Integer> stack = new Stack<>();
30 * for (int i = 0; i < 10; ++i) {
31 * stack.push(i);
32 * }
33 *
34 * for (Integer i = stack.pop(); i != null; i = stack.pop()) {
35 * System.out.println(i);
36 * }
37 * }</pre>
38 *
39 * @author <a href="mailto:franz.wilhelmstoetter@gmx.at">Franz Wilhelmstötter</a>
40 * @version 2.0 — <em>$Date$</em>
41 * @since 2.0
42 */
43 public final class Stack<T> {
44
45 private Node<T> _tail = null;
46
47 public int length = 0;
48
49 public void push(final T value) {
50 _tail = new Node<>(value, _tail);
51 ++length;
52 }
53
54 public T pop() {
55 T value = null;
56 if (_tail != null) {
57 value = _tail._value;
58 _tail = _tail._previous;
59 --length;
60 }
61
62 return value;
63 }
64
65 public void popAll(final Consumer<T> consumer) {
66 for (T element = pop(); element != null; element = pop()) {
67 consumer.accept(element);
68 }
69 }
70
71 public void clear() {
72 _tail = null;
73 length = 0;
74 }
75
76 private static final class Node<T> {
77 final T _value;
78 final Node<T> _previous;
79
80 Node(final T value, final Node<T> previous) {
81 _value = value;
82 _previous = previous;
83 }
84 }
85 }
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