两个栈实现一个队列-Java

package algorithm;

import java.util.LinkedList;
import java.util.Stack;

public class TwoStackImplQueue<T> {

    private Stack<T> stack1;
    private Stack<T> stack2;

    public void push(T value) {
        stack1.push(value);
    }

    public T pop() {
        if (stack2.isEmpty()) {
            for (T val = stack1.pop(); stack1.isEmpty(); ) {
                stack1.push(val);
            }
        }
        return stack1.pop();
    }

    public int size() {
        int len1 = stack1.size();
        int len2 = stack2.size();
        return len1 + len2;
    }
}

class TwoQueueImplStack<T> {
    private LinkedList<T> queue1 = new LinkedList<>();
    private LinkedList<T> queue2 = new LinkedList<>();

    public void push(T val) {
        if (queue1.isEmpty()) {
            queue1.add(val);
        } else {
            queue2.add(val);
        }
    }

    public T pop() {
        if (!queue1.isEmpty()) {
            while (queue1.size() > 0) {
                queue2.addLast(queue1.removeFirst());
            }
            return queue1.removeFirst();
        } else {
            while (queue2.size() > 0) {
                queue1.addLast(queue2.removeFirst());
            }
            return queue2.removeFirst();
        }
    }

    public int size() {
        return queue1.size() + queue2.size();
    }

}