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(1)23     public void EnQueue(int k) throws Exception24     {25         if(s1.isFull())26             throw new Exception("Overflow.");27         else28             s1.push(k);29     }30     31     //时间复杂度: O(n)32     public int DeQueue() throws Exception33     {34         if(s1.isEmpty())35             throw new Exception("Underflow.");36         else37         {38             for(int i = this.s1.getLength(); i > 1; i--)39                 s2.push(s1.pop());40             int key = s1.pop();41             while(!s2.isEmpty())42                 s1.push(s2.pop());43             return key;44         }45     }46 }47 48 class Stack49 {50     private int top;51     private int[] a;52     53     public Stack(int size)54     {55         this.top = -1;56         this.a = new int[size];57     }58     59     public boolean isFull()60     {61         return this.top == this.a.length - 1;62     }63     64     public boolean isEmpty()65     {66         return this.top == -1;67     }68     69     public void push(int k) throws Exception70     {71         /*if(this.isFull())72             throw new Exception("Overflow.");*/73         //else74             this.a[++top] = k;75     }76     77     public int pop() throws Exception78     {79         /*if(this.isEmpty())80             throw new Exception("Underflow.");*/81         //else82             return this.a[top--];83     }84     85     public int getLength()86     {87         return this.top + 1;88     }89 }