java八股文面试[多线程]——线程的状态

5种状态一般是针对传统的线程状态来说（操作系统层面）

6种状态：Java中给线程准备的

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