Java的六种线程状态及代码示例
Java的线程有6个状态，分别是
| State | 状态 | 解释 | 时机 |
| NEW | 新建 | 新建出来的线程 |
执行Thread的start方法前 |
| RUNNABLE | 运行 | 可以细分为运行中和就绪，正在运行或者等待CPU调度。 | 执行Thread的start方法后。yield后。Object.notify、Object.notifyAll、LockSupport.unpark后 |
| BLOCKED | 阻塞 | 还未竞争到的锁的阻塞在那的情况，使用synchronize，但是还没竞争到锁 | 阻塞在synchronize处 |
| WAITING | 等待 | 让出CPU，等待被唤醒 | 调用wait、join、park方法后 |
| TIMED_WAITING | 计时等待 | 让出CPU，等待被唤醒 或者 时间到了自动唤醒 | 调用Thread.sleep(long)、Object.wait(long)、join(long)、LockSupport.parkNanos(long)、LockSupport.parkUntil(long)方法后 |
| TERMINATED | 终止 | 线程的任务执行完成 | 正常执行完成run代码 |
操作系统的线程其实是五种状态，和Java的线程六种状态有些许区别，如下是操作系统的五种线程状态
new 新建状态
runnable 就绪状态
runnning 运行状态
block 阻塞状态，又可以细分为等待阻塞、同步阻塞、其他阻塞，可以大概对应到java中的BLOCKED、WAITING、TIMED_WAITING
dead 死亡状态，就是java中的TERMINATED
如下是Java中线程各个状态的转换图
可以从源码看到这些枚举值
如下是为了加深理解，模拟出的线程的各个状态
public class ThreadStateTest {
public static void main(String[] args) throws InterruptedException {
NEW_RUNNABLE_TERMINATED();
BLOCKED_by_synchronized();
WAITING_by_wait();
WAITING_by_join();
WAITING_by_park();
TIMED_WAITING_by_wait_timeout();
TIMED_WAITING_by_sleep();
TIMED_WAITING_by_join_timeout();
TIMED_WAITING_by_parkUntil();
TIMED_WAITING_by_parkNanos();
}
private static void NEW_RUNNABLE_TERMINATED() throws InterruptedException {
Thread t1 = new Thread(() -> {
while(!Thread.currentThread().isInterrupted()) {
for(long j=0;j<100;j++) {}
}
});
System.out.println("state:" + t1.getState() + " after new");
t1.start();
Thread.sleep(500);
System.out.println("state:" + t1.getState() + " after start");
t1.interrupt();
Thread.sleep(500);
System.out.println("state:" + t1.getState() + " after all");
}
private static void BLOCKED_by_synchronized() throws InterruptedException {
Object o1 = new Object();
Thread t1 = new Thread(() -> {
synchronized (o1) {
}
});
synchronized (o1) {
t1.start();
Thread.sleep(1000);
System.out.println("state:" + t1.getState() + " BLOCKED_by_synchronized");
}
}
private static void WAITING_by_wait() throws InterruptedException {
Object o1 = new Object();
Thread t1 = new Thread(() -> {
synchronized (o1) {
try {
o1.wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
});
t1.start();
Thread.sleep(1000);
System.out.println("state:" + t1.getState() + " WAITING_by_wait");
synchronized (o1) {
o1.notifyAll();
}
}
private static void TIMED_WAITING_by_wait_timeout() throws InterruptedException {
Object o1 = new Object();
Thread t1 = new Thread(() -> {
synchronized (o1) {
try {
o1.wait(2 * 1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
});
t1.start();
Thread.sleep(500);
System.out.println("state:" + t1.getState() + " TIMED_WAITING_by_wait_timeout");
}
private static void WAITING_by_join() throws InterruptedException {
Thread t1 = new Thread(() -> {
try {
Thread.sleep(2 * 1000);
} catch (InterruptedException e) {
throw new RuntimeException(e);
}
});
Thread t2 = new Thread(() -> {
t1.start();
try {
t1.join();
} catch (InterruptedException e) {
throw new RuntimeException(e);
}
});
t2.start();
Thread.sleep(500);
System.out.println("state:" + t2.getState() + " WAITING_by_join");
}
private static void WAITING_by_park() throws InterruptedException {
Thread t1 = new Thread(() -> {
LockSupport.park();
});
t1.start();
Thread.sleep(500);
System.out.println("state:" + t1.getState() + " WAITING_by_park");
Thread.sleep(1000);
LockSupport.unpark(t1);
}
private static void TIMED_WAITING_by_sleep() throws InterruptedException {
Thread t1 = new Thread(() -> {
try {
Thread.sleep(2 * 1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
});
t1.start();
Thread.sleep(500);
System.out.println("state:" + t1.getState() + " TIMED_WAITING_by_sleep");
}
private static void TIMED_WAITING_by_join_timeout() throws InterruptedException {
Thread t1 = new Thread(() -> {
try {
Thread.sleep(4 * 1000);
} catch (InterruptedException e) {
throw new RuntimeException(e);
}
});
Thread t2 = new Thread(() -> {
t1.start();
try {
t1.join(2 * 1000);
} catch (InterruptedException e) {
throw new RuntimeException(e);
}
});
t2.start();
Thread.sleep(500);
System.out.println("state:" + t2.getState() + " TIMED_WAITING_by_join_timeout");
}
private static void TIMED_WAITING_by_parkUntil() throws InterruptedException {
Thread t1 = new Thread(() -> {
long nowMills = System.currentTimeMillis();
LockSupport.parkUntil(2*1000+nowMills);
});
t1.start();
Thread.sleep(500);
System.out.println("state:" + t1.getState() + " TIMED_WAITING_by_parkUntil");
}
private static void TIMED_WAITING_by_parkNanos() throws InterruptedException {
Thread t1 = new Thread(() -> {
LockSupport.parkNanos(TimeUnit.SECONDS.toNanos(2));
});
t1.start();
Thread.sleep(500);
System.out.println("state:" + t1.getState() + " TIMED_WAITING_by_parkNanos");
}
}
wait、join、park