使用栈实现队列(2)(Java)

 1 class MyQueue
 2 {
 3     private Stack s1;
 4     private Stack s2;
 5     
 6     public MyQueue(int size)
 7     {
 8         this.s1 = new Stack(size);
 9         this.s2 = new Stack(size);
10     }
11     
12     public boolean isFull()
13     {
14         return s1.isFull();
15     }
16     
17     public boolean isEmpty()
18     {
19         return s1.isEmpty();
20     }
21     
22     //时间复杂度: O(n)
23     public void EnQueue(int k) throws Exception
24     {
25         if(s1.isFull())
26             throw new Exception("Overflow.");
27         else
28         {
29             while(!s1.isEmpty())
30                 s2.push(s1.pop());
31             s1.push(k);
32             while(!s2.isEmpty())
33                 s1.push(s2.pop());
34         }
35     }
36     
37     //时间复杂度: O(1)
38     public int DeQueue() throws Exception
39     {
40         if(s1.isEmpty())
41             throw new Exception("Underflow.");
42         else
43             return s1.pop();
44     }
45 }
46 
47 class Stack
48 {
49     private int top;
50     private int[] a;
51     
52     public Stack(int size)
53     {
54         this.top = -1;
55         this.a = new int[size];
56     }
57     
58     public boolean isFull()
59     {
60         return this.top == this.a.length - 1;
61     }
62     
63     public boolean isEmpty()
64     {
65         return this.top == -1;
66     }
67     
68     public void push(int k) throws Exception
69     {
70         /*if(this.isFull())
71             throw new Exception("Overflow.");*/
72         //else
73             this.a[++top] = k;
74     }
75     
76     public int pop() throws Exception
77     {
78         /*if(this.isEmpty())
79             throw new Exception("Underflow.");*/
80         //else
81             return this.a[top--];
82     }
83     
84     public int getLength()
85     {
86         return this.top + 1;
87     }
88 }