> For the complete documentation index, see [llms.txt](https://shangan.gitbook.io/algorithm/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://shangan.gitbook.io/algorithm/he-xin-suan-fa-200-ti/hashmap-and-heap/implement-queue-by-two-stack.md).

# Implement Queue by Two Stack

{% tabs %}
{% tab title="Java" %}

```java
public class MyQueue {
    private Stack<Integer> stack1;
    private Stack<Integer> stack2;
    
    public MyQueue() {
        // do intialization if necessary
        stack1 = new Stack<Integer>();
        stack2 = new Stack<Integer>();
    }

    /*
     * @param element: An integer
     * @return: nothing
     */
    public void push(int element) {
        stack1.push(element);
    }

    /*
     * @return: An integer
     */
     
     private void stack1Tostack2(){
         while(!stack1.empty()){
             stack2.push(stack1.peek());
             stack1.pop();
         }
     }
     
    public int pop() {
        // write your code here
        if(stack2.empty()){
            stack1Tostack2();
        }
        return stack2.pop();
    }

    /*
     * @return: An integer
     */
    public int top() {
        // write your code here
        if(stack2.empty()){
            stack1Tostack2();
        }
        return stack2.peek();
    }
}
```

{% endtab %}
{% endtabs %}

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