線程6種狀態：
- NEW
Thread state for a thread which has not yet started.
- RUNNABLE
Thread state for a runnable thread. A thread in the runnable state is executing in the Java virtual machine but it may be waiting for other resources from the operating system such as processor.
- BLOCKED
Thread state for a thread blocked waiting for a monitor lock. A thread in the blocked state is waiting for a monitor lock to enter a synchronized block/method or reenter a synchronized block/method after calling Object.wait.
- WAITING
Thread state for a waiting thread. A thread is in the waiting state due to calling one of the following methods:
- Object.wait with no timeout
- Thread.join with no timeout
- LockSupport.park
A thread in the waiting state is waiting for another thread to perform a particular action. For example, a thread that has called Object.wait() on an object is waiting for another thread to call Object.notify() or Object.notifyAll() on that object. A thread that has called Thread.join() is waiting for a specified thread to terminate.
- TIME_WAITING
Thread state for a waiting thread with a specified waiting time. A thread is in the timed waiting state due to calling one of the following methods with a specified positive waiting time:
- Thread.sleep
- Object.wait with timeout
- Thread.join with timeout
- LockSupport.parkNanos
- LockSupport.parkUntil
- TERMINATED
Thread state for a terminated thread. The thread has completed execution.
代碼模擬線程的6種狀態
public class ThreadState {
public static void main(String[] args) throws Exception {
Thread t1 = new Thread(() ->{
System.out.println("2:"+Thread.currentThread().getState());
for (int i = 0;i < 3;i++){
SleepHelp1.sleepseconds(1);
System.out.print(i+" ");
}
System.out.println();
});
System.out.println("1:"+t1.getState());
t1.start();
t1.join();
System.out.println("3:"+t1.getState());
//=====================================================================
Thread t2 = new Thread(()->{
//阻塞 等着被叫醒 waiting
LockSupport.park();
System.out.println("t2 go on");
SleepHelp1.sleepseconds(5);
});
t2.start();
SleepHelp1.sleepseconds(1);
System.out.println("4:"+t2.getState());
//叫醒線程
LockSupport.unpark(t2);
SleepHelp1.sleepseconds(1);
System.out.println("5:"+t2.getState());
//=====================================================================
final Object o = new Object();
Thread t3 = new Thread(()->{
synchronized (o){
System.out.println("t3 得到了 鎖 o");
}
});
new Thread(()->{
synchronized (o){
SleepHelp1.sleepseconds(5);
}
}).start();
SleepHelp1.sleepseconds(1);
t3.start();
SleepHelp1.sleepseconds(1);
System.out.println("6:"+t3.getState());
//===========================================================
//juc的鎖 盲等待， 不會進入 block 的狀態，進入 waiting 狀態
final Lock lock = new ReentrantLock();
Thread t4 = new Thread(()->{
lock.lock();//省略掉 try ... finally
System.out.println("t4 拿到了鎖 o");
lock.unlock();
});
new Thread(()->{
lock.lock();
SleepHelp1.sleepseconds(5);
lock.unlock();
}).start();
SleepHelp1.sleepseconds(1);
t4.start();
SleepHelp1.sleepseconds(1);
System.out.println("7:"+t4.getState());
//=======================================================
Thread t5 = new Thread(()->{
LockSupport.park();
});
t5.start();
SleepHelp1.sleepseconds(1);
System.out.println("8:"+t5.getState());
SleepHelp1.sleepseconds(1);
LockSupport.unpark(t5);
}
}
class SleepHelp1 {
public static void sleepseconds(int seconds){
try {
TimeUnit.SECONDS.sleep(seconds);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
執行結果：
1:NEW
2:RUNNABLE
0 1 2
3:TERMINATED
4:WAITING
t2 go on
5:TIMED_WAITING
6:BLOCKED
7:WAITING
t3 得到了 鎖 o
8:WAITING
t4 拿到了鎖 o
