三个线程按顺序打印abc

package com.company;


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

public class Main {


    public static void main(String[] args) throws InterruptedException {
        Queue wordList = new LinkedList();
        Object todoA = new Object();
        Object todoB = new Object();
        Object todoC = new Object();
        for (int i = 0; i < 100; i++) {
            wordList.add('a');
            wordList.add('b');
            wordList.add("c ");
        }
        new Thread(new PrintWord("1", wordList, todoA, todoB)).start();
        new Thread(new PrintWord("2", wordList, todoB, todoC)).start();
        new Thread(new PrintWord("3", wordList, todoC, todoA)).start();
        synchronized (todoA) {
            todoA.notify();
        }

        // write your code here
    }

    public static class PrintWord implements Runnable {
        String id;
        Queue wordList;
        Object todo;
        Object todoNext;

        private PrintWord(String id, Queue wordList, Object todo, Object todoNext) {
            this.id = id;
            this.wordList = wordList;
            this.todo = todo;
            this.todoNext = todoNext;

        }

        @Override
        public void run() {
            while (true) {
                try {
                    synchronized (todo) {
                        todo.wait();
                        Object _word = wordList.peek();
                        if (_word != null) {
                            System.out.print(this.id);
                            System.out.print(_word);
                            wordList.remove();
                        }
                        synchronized (todoNext) {
                            todoNext.notifyAll();
                        }
                        if (_word == null) break;
                    }
                } catch (InterruptedException e) {
                    synchronized (todoNext) {
                        todoNext.notifyAll();
                    }
                    e.printStackTrace();
                }
            }

        }
    }
}