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20 package org.apache.mina.util;
21
22 import java.io.Serializable;
23 import java.util.Arrays;
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31 public class Stack implements Serializable {
32 private static final long serialVersionUID = 3546919169401434168L;
33
34 private static final int DEFAULT_CAPACITY = 4;
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36 private Object[] items;
37
38 private int size = 0;
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42
43 public Stack() {
44 items = new Object[DEFAULT_CAPACITY];
45 }
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49
50 public void clear() {
51 Arrays.fill(items, null);
52 size = 0;
53 }
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60
61 public Object pop() {
62 if (size == 0) {
63 return null;
64 }
65
66 int pos = size - 1;
67 Object ret = items[pos];
68 items[pos] = null;
69 size--;
70
71 return ret;
72 }
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74
75
76
77 public void push(Object obj) {
78 if (size == items.length) {
79
80 final int oldLen = items.length;
81 Object[] tmp = new Object[oldLen * 2];
82 System.arraycopy(items, 0, tmp, 0, size);
83 items = tmp;
84 }
85
86 items[size] = obj;
87 size++;
88 }
89
90 public void remove(Object o) {
91 for (int i = size - 1; i >= 0; i--) {
92 if (items[i] == o) {
93 System.arraycopy(items, i + 1, items, i, size - i - 1);
94 items[size - 1] = null;
95 size--;
96 break;
97 }
98 }
99 }
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107 public Object first() {
108 if (size == 0) {
109 return null;
110 }
111
112 return items[size - 1];
113 }
114
115 public Object last() {
116 if (size == 0) {
117 return null;
118 }
119
120 return items[0];
121 }
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126 public boolean isEmpty() {
127 return (size == 0);
128 }
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133 public int size() {
134 return size;
135 }
136 }