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13public
14class Stack2
15extends java.util.Vector
16implements StackInterface {
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22 public
23 Stack2() {
24 super();
25 }
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40 public
41 Object top()
42 {
43 assert preTop() : "Stack2.top: empty stack";
44
45 return
46 lastElement();
47 }
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51 public
52 void push(Object o) {
53 addElement(o);
54 }
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58 public
59 void pop()
60 {
61 assert prePop() : "Stack2.pop: empty stack";
62
63 removeElementAt(elementCount-1);
64 }
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71 public
72 boolean prePop() {
73 return
74 ! isEmpty();
75 }
76
77 public
78 boolean preTop() {
79 return
80 ! isEmpty();
81 }
82
83}
84
85
