java线程之一：线程的生命周期

1：先说基本概念：线程状态：新建状态 ------》就绪状态-----》运行状态----》死亡状态

新建状态：使用 new 关键字和 Thread 类或其子类建立一个线程对象后，该线程对象就处于新建状态

就绪状态：当线程对象调用了start()方法之后，该线程就进入就绪状态。就绪状态的线程处于就绪队列中，要等待JVM里线程调度器的调度

运行状态：如果就绪状态的线程获取 CPU 资源，就可以执行 run()，此时线程便处于运行状态。处于运行状态的线程最为复杂，它可以变为阻塞状态、就绪状态和死亡状态

阻塞线程： 线程调用：sleep() join() wait()会变成阻塞状态

死亡状态：任务执行完毕，或者调用线程stop()函数

2：实际代码（待完成）

1： join函数的实现：中断当前线程，将Cpu控制权交给，join线程，jion线程业务执行完毕，继续执行当前线程逻辑

public class ThreadDemo {
    public static void main(String[] args) throws InterruptedException {
        System.out.println("thread name  = " + Thread.currentThread().getName());
        Thread thread = new Thread(new MyRunnable(), "thread1");
        thread.start();
        for(int i = 0; i< 5 ; i++) {
            System.out.println("thread name  = " + Thread.currentThread().getName() + "--i = " + i);
            if (i == 2) {
                thread.join();
            }
        }
    }

    private static class MyRunnable implements Runnable {
        @Override
        public void run() {
            System.out.println("thread name  = " + Thread.currentThread().getName());
            for (int j = 0 ; j<3;j++) {
                System.out.println("thread name  = " + Thread.currentThread().getName() + "--j = " + j);
            }
        }
    }
}

sleep函数：阻塞当前线程，阻塞期间不释放锁，释放CPU资源

public class ThreadDemoForSleep {
    public static void main(String[] args) throws InterruptedException {
        System.out.println("thread name  = " + Thread.currentThread().getName());
        Thread thread = new Thread(new MyRunnable(), "thread1");
        for (int i = 0; i < 100; i++) {
            System.out.println("thread name  = " + Thread.currentThread().getName() +
                    "--i = " + i + ", system time = " +
                    DateFormatUtils.formatDate(System.currentTimeMillis()));
            if (i == 2) {
                sleep(5000); // 休眠20s (主线程阻塞20s后自动唤醒,阻塞期间不释放cpu)
                thread.start();
            }
        }
    }
    private static class MyRunnable implements Runnable {
        @Override
        public void run() {
            System.out.println("thread name  = " + Thread.currentThread().getName() +
                    ", system time = " + DateFormatUtils.formatDate(System.currentTimeMillis()));
            for (int j = 0; j < 3; j++) {
                System.out.println("thread name  = " + Thread.currentThread().getName() + "--j = " + j);
            }
        }
    }
}

wait : 因为wait需释放锁，所以必须在synchronized中使用（没有锁定可以释放吗？答：没有锁时使用会抛出IllegalMonitorStateException ，不可用代用wait()）

public class ThreadDemoForWait {
    public static void main(String[] args) throws InterruptedException {
        System.out.println("main thread name  enter = " + Thread.currentThread().getName());
        MyThread thread = new MyThread( "waitThread");
        synchronized (thread) {
            // 启动 waitThread 线程
            thread.start();
            // 阻塞主线程，等待其他线程唤醒
            System.out.println("main thread name is waited");
            thread.wait();
            for (int j = 0; j < 3; j++) {
                System.out.println(" main thread notifyed = " +
                        Thread.currentThread().getName() + "--j = " + j);
            }
        }
    }

    private static class MyThread extends Thread {
        public MyThread(String threadName) {
            super(threadName);
        }
        @Override
        public void run() {
            synchronized (this) {
                System.out.println("waitThread name enter = " + Thread.currentThread().getName());
                for (int j = 0; j < 3; j++) {
                    System.out.println("thread name  = " + Thread.currentThread().getName() + "--j = " + j);
                }
                System.out.println("waitThread start sleep  = " +
                        DateFormatUtils.formatDate(System.currentTimeMillis()));
                try {
                    // 当前线程休眠2s
                    Thread.sleep(2000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                // 休眠时间结束，唤醒执行wait()函数的线程（主线程）
                System.out.println("waitThread sleep ended = " +
                        DateFormatUtils.formatDate(System.currentTimeMillis()));
                notify();
            }

        }
    }

3：流程图（待完成）

4：项目实际用到了没有

java线程之一：线程的生命周期

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