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15public
16class SimpleStack {
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24 private
25 Object[] elems;
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32 private
33 int top;
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44 public
45 SimpleStack(int max) {
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47 elems = new Object[max];
48 top = 0;
49 }
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53 public
54 SimpleStack() {
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56 this(20);
57 }
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65 public
66 boolean isEmpty() {
67 return
68 top == 0;
69 }
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77 public
78 Object top()
79 {
80 return
81 elems[top - 1];
82 }
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90 public
91 void push(Object o) {
92 elems[top++] = o;
93 }
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103 public
104 void pop()
105 {
106 elems[--top] = null;
107 }
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121 public
122 boolean prePop() {
123 return
124 ! isEmpty();
125 }
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127 public
128 boolean preTop() {
129 return
130 ! isEmpty();
131 }
132}
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134
