cc150_3_5.java

package cc150_3_5;

import java.util.Stack;

public class StackQueue<T> {
	
	private Stack<T> origin;
	private Stack<T> reverse;
	
	public StackQueue(){
		origin = new Stack<>();
		reverse = new Stack<>() ;
	}
	
    public void Insert(T item) {
    	origin.push(item);
    }
	
    public int size() {
        return origin.size()+reverse.size();
    }
	
    public T Deque() {
    	if (reverse.isEmpty()) {
    	    while (!origin.isEmpty()) {
    		reverse.push(origin.pop());
    	    }
    	}
    	if (reverse.isEmpty())
    	    return null;
    	return reverse.pop();
    }
    
    
    public boolean isEmpty() {
	return origin.isEmpty() && reverse.isEmpty();
    }

	
    public static void main(String[] args) {
	StackQueue<Integer> queue = new StackQueue<>();
	for (int i = 1; i <= 10; i++)
	    queue.Insert(i);
 
	for (int i = 1; i <= 5; i++)
	    System.out.println("Dequeue: " + queue.Deque());
 
	for (int i = 11; i <= 15; i++)
	    queue.Insert(i);
 
	while (!queue.isEmpty())
	    System.out.println("Dequeue: " + queue.Deque());
	//test dequeue empty stack
	System.out.println("Dequeue: " + queue.Deque());
    }

}