【多线程的应用】顺序打印

题目

class Thread_2252 {// 计数器private static volatile int COUNTER = 0;// 定义一个单独的锁对象private static Object lock = new Object();public static void main(String[] args) {// 创建三个线程，并指定线程名，每个线程名分别用A,B,C表示Thread t1 = new Thread(() -> {// 循环10次for (int i = 0; i < 10; i++) {// 执行的代码加锁synchronized (lock) {// 每次唤醒后都重新判断是否满足条件// 每条线程判断的条件不一样，注意线程t1,t2while (COUNTER % 3 != 0) {try {// 不满足输出条件时，主动等待并释放锁lock.wait();} catch (InterruptedException e) {e.printStackTrace();}}// 满足输出条件，打印线程名，每条线程打印的内容不同System.out.print(Thread.currentThread().getName());// 累加计数COUNTER++;// 唤醒其他线程lock.notifyAll();}}}, "A");Thread t2 = new Thread(() -> {for (int i = 0; i < 10; i++) {synchronized (lock) {while (COUNTER % 3 != 1) {try {lock.wait();} catch (InterruptedException e) {e.printStackTrace();}}System.out.print(Thread.currentThread().getName());COUNTER++;lock.notifyAll();}}}, "B");Thread t3 = new Thread(() -> {for (int i = 0; i < 10; i++) {synchronized (lock) {while (COUNTER % 3 != 2) {try {lock.wait();} catch (InterruptedException e) {e.printStackTrace();}}// 换行打印System.out.println(Thread.currentThread().getName());COUNTER++;lock.notifyAll();}}}, "C");// 启动线程t1.start();t2.start();t3.start();}
}

注意点：

1. 每个线程循环10次，利用锁的wait 和 计数器count

调节线程的执行顺序

2. count++后 lock.notifyAll 唤醒所有线程

3. Thread.currentThread().getName()

4. 锁中的逻辑是：进入锁中后，如果while不

满足 那就wait，count++所有wait唤醒，再判断count

当然每次一定是 解锁一个wait 其余在while继续wait

2. 多线程的顺序打印

同时启动的话，那么每个线程中 join一下优先打印的

public class Thread_2152 {public static void main(String[] args) throws InterruptedException {// 创建三个线程Thread tc = new Thread(() -> {// 打印cSystem.out.print(Thread.currentThread().getName() + " ");}, "c");Thread tb = new Thread(() -> {try {// 等待c 执行完成tc.join();} catch (InterruptedException e) {e.printStackTrace();}// 打印bSystem.out.print(Thread.currentThread().getName() + " ");}, "b");Thread ta = new Thread(() -> {try {// 等待b 执行完成tb.join();} catch (InterruptedException e) {e.printStackTrace();}// 打印aSystem.out.print(Thread.currentThread().getName() + " ");}, "a");// 需要让他们同时启动，并按 c，b，a的顺序打印ta.start();tb.start();tc.start();}
}