一、线程状态的种类及含义

线程的状态是个枚举类型Thread.State

public class ThreadState{public static void main(String []args){for(Thread.State state:Thread.State.values()){System.out.println(state);}}
}

1.NEW：安排了工作，还未开始行动

2.RUNNABLE:可工作的，分成正在工作中和即将开始工作。类似于进程中的就绪和运行状态。

3.BLOCKED:表示排队等待其他事情。同步阻塞，因为资源竞争而引起的阻塞。

4.WAITING:表示排队等待其他事情。等待阻塞，join()，需要其他线程唤醒。

5.TIMED_WAITING:表示排队等待其他事情。计时等待阻塞，有一定的等待时间。

6.TERMINATED:工作完成。

二、线程状态间的切换条件

（1）使用isAlive()判断线程的存活状态

public class ThreadStateTransfer {public static void main(String[] args) throws InterruptedException {Thread t = new Thread(() -> {for (int i = 0; i <1; i++) {}}, "线程一");System.out.println(t.getName() + ": " + t.getState());t.start();while (t.isAlive()) {System.out.println(t.getName() + ": " + t.getState());}System.out.println(t.getName() + ": " + t.getState());;}
}

（2）关于BLOCKED、WAITING、TIMED_WAITING状态之间的转换

1.TIMED_WAITING

public class ThreadStateTransfer {public static void main(String[] args) {final Object object = new Object();Thread t1 = new Thread(new Runnable() {@Overridepublic void run() {synchronized (object) {while (true) {try {Thread.sleep(1000);} catch (InterruptedException e) {e.printStackTrace();}}}}}, "t1");t1.start();Thread t2 = new Thread(new Runnable() {@Overridepublic void run() {synchronized (object) {System.out.println("hehe");}}}, "t2");t2.start();}
}

代码中使用Thread.sleep（10000），此时线程t1是TIMED_WAITING状态，而t2则是BLOCKED转态。

2.WAITING

public class ThreadStateTransfer {public static void main(String[] args) {final Object object = new Object();Thread t1 = new Thread(new Runnable() {@Overridepublic void run() {synchronized (object) {while (true) {try {object.wait();} catch (InterruptedException e) {e.printStackTrace();}}}}}, "t1");t1.start();Thread t2 = new Thread(new Runnable() {@Overridepublic void run() {synchronized (object) {System.out.println("hehe");}}}, "t2");t2.start();}
}