多线程顺序执行

[java]代码库

package app;

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

public class App {
    public static void main(String[] args) {
        new Thread(new Runner(0)).start();
        new Thread(new Runner(1)).start();
        new Thread(new Runner(2)).start();
        new Thread(new Runner(3)).start();
    }

    static class Runner implements Runnable {
        int no;
        static Queue<Character> queue = new LinkedList<>();

        static {
            for (int i = 0; i < 10; i++) {
                queue.offer('A');
                queue.offer('B');
                queue.offer('C');
                queue.offer('D');
            }
        }

        Runner(int no) {
            this.no = no;
        }

        @Override
        public void run() {
            while (queue.size() != 0) {
                synchronized (queue) {
                    if (queue.size() != 0 && no == (40 - queue.size()) % 4) {
                        System.out.println(queue.poll());
                    }
                }
            }
        }
    }
}