java八股文面试[多线程]——线程的状态

刺骨的言语ヽ痛彻心扉 2024-03-26 22:56 22阅读 0赞

**5种状态**一般是针对**传统的**线程状态来说（**操作系统**层面）

![image.png][]

**6种状态**：Java中给线程准备的

![image.png][image.png 1]

NEW：Thread对象被创建出来了，但是还没有执行start方法。

RUNNABLE：Thread对象调用了start方法，就为RUNNABLE状态（CPU调度/没有调度）

BLOCKED、WAITING、TIME\_WAITING：都可以理解为是阻塞、等待状态，因为处在这三种状态下，CPU不会调度当前线程

BLOCKED：synchronized没有拿到同步锁，被阻塞的情况

WAITING：调用wait方法就会处于WAITING状态，需要被手动唤醒

TIME\_WAITING：调用sleep方法或者join方法，会被自动唤醒，无需手动唤醒

TERMINATED：run方法执行完毕，线程生命周期到头了

**在Java代码中验证一下效果**

NEW：

public static void main(String[] args) throws InterruptedException {
        Thread t1 = new Thread(() -> {
      
        });
        System.out.println(t1.getState());
    }

RUNNABLE：

public static void main(String[] args) throws InterruptedException {
        Thread t1 = new Thread(() -> {
            while(true){
    
            }
        });
        t1.start();
        Thread.sleep(500);
        System.out.println(t1.getState());
    }

BLOCKED：

public static void main(String[] args) throws InterruptedException {
        Object obj = new Object();
        Thread t1 = new Thread(() -> {
            // t1线程拿不到锁资源，导致变为BLOCKED状态
            synchronized (obj){
    
            }
        });
        // main线程拿到obj的锁资源
        synchronized (obj) {
            t1.start();
            Thread.sleep(500);
            System.out.println(t1.getState());
        }
    }

WAITING：

public static void main(String[] args) throws InterruptedException {
        Object obj = new Object();
        Thread t1 = new Thread(() -> {
            synchronized (obj){
                try {
                    obj.wait();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        });
        t1.start();
        Thread.sleep(500);
        System.out.println(t1.getState());
    }

TIMED\_WAITING：

public static void main(String[] args) throws InterruptedException {
        Thread t1 = new Thread(() -> {
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        });
        t1.start();
        Thread.sleep(500);
        System.out.println(t1.getState());
    }

TERMINATED：

public static void main(String[] args) throws InterruptedException {
        Thread t1 = new Thread(() -> {
            try {
                Thread.sleep(500);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        });
        t1.start();
        Thread.sleep(1000);
        System.out.println(t1.getState());
    }

知识来源：

[【2023年面试】Java面向对象有哪些特征\_哔哩哔哩\_bilibili][2023_Java_bilibili]

[image.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/11/a17a6ff56f144df8aaadff88a1f68caf.png
[image.png 1]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/11/f13bd2d740c242bab7738ac5d1092ff9.png
[2023_Java_bilibili]: https://www.bilibili.com/video/BV1Vb4y177wm/?p=1&vd_source=7ec3a2ec18181a9b64c9a3246305e511