Queue 2개로 Stack구현하기

Queue 2개로 Stack구현하기

import java.util.LinkedList;
import java.util.Queue;

public class Stack<T> {
  private Queue<T> q1;
  private Queue<T> q2;

  public Stack() {
    this.q1 = new LinkedList<>();
    this.q2 = new LinkedList<>();
  }

  public void push(T value) {
    q1.add(value);
  }

  public T pop() {
    while (q1.size() > 1) {
      q2.add(q1.poll());
    }

    Queue<T> temp = q1;
    q1 = q2;
    q2 = temp;
    return q2.poll();
  }

  @Override
  public String toString() {
    return "Stack{" +
        "q1=" + q1 +
        ", q2=" + q2 +
        '}';
  }

  public static void main(String[] args) {
    Stack<Integer> stack = new Stack<>();
    stack.push(1);
    stack.push(2);
    stack.push(3);
    stack.push(4);
    stack.push(5);

    System.out.println(stack.pop());
    System.out.println(stack);
    System.out.println(stack.pop());
    System.out.println(stack);
  }
}