A queue of two stacks

subject ： Write a class , Queues are implemented with two stacks , Support the basic operation of queue

answer ： Stack is first in, first out , The queue is in and out . With two stacks , You must require the reverse order of all the numbers in one stack from another stack . Such a stack is only responsible for pressing , The other stack is only responsible for ejecting .

But be careful , You have to wait until all the elements are completely on a stack , Can operate on another stack , Make the order of elements in it opposite to the first stack . And if the second stack is not empty , It can't be operated on .

See code for specific implementation ：

package text2;

import java.util.Stack;

public class TwoStackQueue {
	public Stack<Integer> stackpush;
	public Stack<Integer> stackpop;
	public TwoStackQueue() {
		stackpush=new Stack<Integer>();
		stackpop=new Stack<Integer>();
	}
	
	private void pushToPop() {
		if (stackpop.empty()) {
			while(!stackpush.empty()) {
				stackpop.push(stackpush.pop());
			}
		}
	}
	public void add(int pushint) {
		stackpush.push(pushint);
		pushToPop();
	}
	public int poll() {
		if(stackpop.empty()&&stackpush.empty()) {
			throw new RuntimeException("Queue is empty.");
		}
		pushToPop();
		return stackpop.pop();
	}
	public int peek() {
		if(stackpop.empty()&&stackpush.empty()) {
			throw new RuntimeException("Queue is empty.");
		}
		pushToPop();
		return stackpop.peek();
	}

}

In the above code , Stack used empty() and isempty() There is no difference between the two functions . That is, when the stack is empty , Use both functions .

But there is only isempty Method .