目录
- 1、线程状态分类
- 2、状态详解
- 2.1、状态 1：NEW
- 2.2、状态 2：RUNNABLE
- 2.3、状态 3：BLOCKED
- 2.4、状态 4：WAITING
- 2.5、状态 5：TIMED_WAITING
- 2.6、状态 6：TERMINATED
- 3、状态转换图
- 最新资料
1、线程状态分类
线程一共有六种状态，分别为 New、RUNNABLE、BLOCKED、WAITING、TIMED_WAITING、TERMINATED，同一时刻只有一种状态，通过线程的 getState 方法可以获取线程的状态。2、状态详解
Thread 的状态使用 java.lang.Thread.State 枚举表示。2.1、状态 1：NEW
当线程被创建出来还没有被调用 start()时候的状态。
public class NewState {
public static void main(String[] args) {
Thread thread1 = new Thread(“thread1”);
System.out.println(thread1.getState());
}
}
输出
NEW
2.2、状态 2：RUNNABLE
当线程被调用了 start()，且处于等待操作系统分配资源（如 CPU）、等待 IO 连接、正在运行状态，即表示 Running 状态和 Ready 状态。
注：不一定被调用了 start()立刻会改变状态，还有一些准备工作，这个时候的状态是不确定的。
public class RunnableState {
public static void main(String[] args) {
Thread thread1 = new Thread(“thread1”);
thread1.start();
System.out.println(thread1.getState());
}
}
输出
RUNNABLE
2.3、状态 3：BLOCKED
等待监视器锁而被阻塞的线程的线程状态，当进入 synchronized 块/方法或者在调用 wait()被唤醒/超时之后重新进入 synchronized 块/方法，但是锁被其它线程占有，这个时候被操作系统挂起，状态为阻塞状态。
阻塞状态的线程，即使调用 interrupt()方法也不会改变其状态。
下面看案例代码，thread1 持有 lock 对象的锁一直没有释放，而 thread2 也想获取 lock 对象的锁，但是锁一直被 thread1 持有者，导致 thread2 被阻塞在@1 处，此时 thread2 的状态就是 BLOCKED 状态。
import java.util.concurrent.TimeUnit;
public class BlockedState {
static String lock = “锁”;
**public** **static** **void** **main**(String[] args) **throws** InterruptedException {<br /> Thread thread1 = **new** Thread("thread1") {<br /> @Override<br /> **public** **void** **run**() {<br /> **synchronized** (lock) {<br /> //死循环导致thread1一直持有lock对象锁<br /> **while** (**true**) ;<br /> }<br /> }<br /> };<br /> thread1.start();//休眠1秒，让thread1先启动<br /> TimeUnit.SECONDS.sleep(1);Thread thread2 = **new** Thread("thread2") {<br /> @Override<br /> **public** **void** **run**() {<br /> **synchronized** (lock) { //@1<br /> System.out.println("thread2");<br /> }<br /> }<br /> };<br /> thread2.start();System.out.println("thread1.state:" + thread1.getState());<br /> System.out.println("thread2.state:" + thread2.getState());}<br />}
运行结果
thread1.state:RUNNABLE
thread2.state:BLOCKED
2 个线程的堆栈信息，线程堆栈信息中包含了线程的详细信息，如：线程状态、线程目前执行到哪段代码了
“thread2” #13 prio=5 os_prio=0 tid=0x00000000281ec000 nid=0x878 waiting for monitor entry [0x0000000028dff000]
java.lang.Thread.State: BLOCKED (on object monitor)
at BlockedState$2.run(BlockedState.java:25)
- waiting to lock <0x00000007176b2a20> (a java.lang.String)
Locked ownable synchronizers:
- None
“thread1” #12 prio=5 os_prio=0 tid=0x00000000281ea800 nid=0x5e50 runnable [0x0000000028cff000]
java.lang.Thread.State: RUNNABLE
at BlockedState$1.run(BlockedState.java:12)
- locked <0x00000007176b2a20> (a java.lang.String)
Locked ownable synchronizers:
- None
2.4、状态 4：WAITING
无条件等待，当线程调用 wait()/join()/LockSupport.park()不加超时时间的方法之后所处的状态，如果没有被唤醒或等待的线程没有结束，那么将一直等待，当前状态的线程不会被分配 CPU 资源和持有锁.
简单理解：就是无限期等待。
导致线程处于 WAITING 有 3 中方式。
方式 1：wait()
import java.util.concurrent.TimeUnit;
public class WaitingState1 {
public static void main(String[] args) throws InterruptedException {
Thread thread1 = new Thread(“thread1”) {
@Override
public void run() {
synchronized (WaitingState1.class) {
try {
//调用wait方法，让线程等待
WaitingState1.class.wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
};
thread1.start();
//模拟休眠1秒，让thread1运行到wait方法处
TimeUnit.SECONDS.sleep(1);
System.out.println(“thread.state:” + thread1.getState());
}
}
输出
thread1.state:WAITING
线程 thread1 堆栈信息
“thread1” #12 prio=5 os_prio=0 tid=0x0000000027a5d800 nid=0x1b48 in Object.wait() [0x0000000028dbe000]
java.lang.Thread.State: WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
- waiting on <0x00000007176adc68> (a java.lang.Class for WaitingState1)
at java.lang.Object.wait(Object.java:502)
at WaitingState1$1.run(WaitingState1.java:11)
- locked <0x00000007176adc68> (a java.lang.Class for WaitingState1)
Locked ownable synchronizers:
- None
方式 2：join()
public class WaitingState2 {
public static void main(String[] args) throws InterruptedException {
Thread thread1 = new Thread(“thread1”) {
@Override
public void run() {
while (true) ;
}
};
thread1.start();
//join方法会让当前主线程等待thread1结束
thread1.join();
}
}
上面代码会导致主线程处于 WAITING 状态，下面是主线程堆栈信息，第 2 行显示主线程处于 WAITING 状态
“main” #1 prio=5 os_prio=0 tid=0x00000000035a4000 nid=0x3fbc in Object.wait() [0x000000000305f000]
java.lang.Thread.State: WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
- waiting on <0x00000007176b0708> (a WaitingState2$1)
at java.lang.Thread.join(Thread.java:1249)
- locked <0x00000007176b0708> (a WaitingState2$1)
at java.lang.Thread.join(Thread.java:1323)
at WaitingState2.main(WaitingState2.java:14)
Locked ownable synchronizers:
- None
方式 3：LockSupport.park()
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.LockSupport;
public class WaitingState3 {
public static void main(String[] args) throws InterruptedException {
Thread thread1 = new Thread(“thread1”) {
@Override
public void run() {
LockSupport.park();
}
};
thread1.start();
//模拟休眠1秒，让thread1运行到park方法处
TimeUnit.SECONDS.sleep(1);
System.out.println(“thread1.state:” + thread1.getState());
}
}
输出
thread1.state:WAITING
线程 thread1 堆栈信息
“thread1” #12 prio=5 os_prio=0 tid=0x00000000287cc000 nid=0x3880 waiting on condition [0x000000002918f000]
java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:304)
at WaitingState3$1.run(WaitingState3.java:9)
Locked ownable synchronizers:
- None
2.5、状态 5：TIMED_WAITING
有条件的等待，当线程调用 sleep(睡眠时间)/wait(等待时间)/join(等待时间)/ LockSupport.parkNanos(等待时间)/LockSupport.parkUntil(等待时间)方法之后所处的状态，在指定的时间没有被唤醒或者等待线程没有结束，会被系统自动唤醒，正常退出。
简单点理解：有限期等待。
导致线程处于 WAITING 有 5 中方式。
方式 1：sleep(睡眠时间)
import java.util.concurrent.TimeUnit;
public class TimedWaitingState1 {
public static void main(String[] args) throws InterruptedException {
Thread thread1 = new Thread(“thread1”) {
@Override
public void run() {
//休眠500秒 = 500000毫秒
try {
Thread.sleep(500 1000);
} *catch (InterruptedException e) {
e.printStackTrace();
}
}
};
thread1.start();
//模拟休眠1秒，让thread1运行到sleep方法处
TimeUnit.SECONDS.sleep(1);
System.out.println(“thread1.state:” + thread1.getState());
}
}
输出
thread1.state:TIMED_WAITING
线程 thread1 堆栈信息，堆栈信息中可以看出是线程 sleep 方法导致线程等待的
“thread1” #12 prio=5 os_prio=0 tid=0x0000000027e1c000 nid=0x5c68 waiting on condition [0x000000002917f000]
java.lang.Thread.State: TIMED_WAITING (sleeping)
at java.lang.Thread.sleep(Native Method)
at TimedWaitingState1$1.run(TimedWaitingState1.java:10)
Locked ownable synchronizers:
- None
方式 2：wait(等待时间)
import java.util.concurrent.TimeUnit;
public class TimedWaitingState2 {
public static void main(String[] args) throws InterruptedException {
Thread thread1 = new Thread(“thread1”) {
@Override
public void run() {
synchronized (TimedWaitingState2.class) {
try {
//调用wait方法，让线程等待500秒
TimedWaitingState2.class.wait(500 1000);
} *catch (InterruptedException e) {
e.printStackTrace();
}
}
}
};
thread1.start();
//模拟休眠1秒，让thread1运行到wait方法处
TimeUnit.SECONDS.sleep(1);
System.out.println(“thread1.state:” + thread1.getState());
}
}
输出
thread1.state:TIMED_WAITING
线程 thread1 堆栈信息，堆栈信息中可以看出是线程 wait 方法导致线程等待的
“thread1” #12 prio=5 os_prio=0 tid=0x0000000028571000 nid=0x4b80 in Object.wait() [0x0000000028f2e000]
java.lang.Thread.State: TIMED_WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
- waiting on <0x00000007176ae0b8> (a java.lang.Class for TimedWaitingState2)
at TimedWaitingState2$1.run(TimedWaitingState2.java:11)
- locked <0x00000007176ae0b8> (a java.lang.Class for TimedWaitingState2)
Locked ownable synchronizers:
- None
方式 3：join(等待时间)
public class TimedWaitingState3 {
public static void main(String[] args) throws InterruptedException {
Thread thread1 = new Thread(“thread1”) {
@Override
public void run() {
while (true) ;
}
};
thread1.start();
//join方法会让当前主线程等待thread1结束，最长等待500s，如果500s
thread1.join(500 * 1000);
}
}
主线程堆栈信息
“main” #1 prio=5 os_prio=0 tid=0x0000000003274000 nid=0x1204 in Object.wait() [0x00000000030ee000]
java.lang.Thread.State: TIMED_WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
- waiting on <0x00000007176b0cf8> (a TimedWaitingState3$1)
at java.lang.Thread.join(Thread.java:1257)
- locked <0x00000007176b0cf8> (a TimedWaitingState3$1)
at TimedWaitingState3.main(TimedWaitingState3.java:11)
Locked ownable synchronizers:
- None
方式 4：LockSupport.parkNanos(等待时间)
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.LockSupport;
public class TimedWaitingState4 {
public static void main(String[] args) throws InterruptedException {
Thread thread1 = new Thread(“thread1”) {
@Override
public void run() {
//等待500秒
LockSupport.parkNanos(TimeUnit.SECONDS.toNanos(500));
}
};
thread1.start();
//模拟休眠1秒，让thread1运行到parkNanos方法处
TimeUnit.SECONDS.sleep(1);
System.out.println(“thread1.state:” + thread1.getState());
}
}
输出
thread1.state:TIMED_WAITING
线程 thread1 堆栈信息
“thread1” #12 prio=5 os_prio=0 tid=0x0000000028a1e000 nid=0x455c waiting on condition [0x00000000293ff000]
java.lang.Thread.State: TIMED_WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
at java.util.concurrent.locks.LockSupport.parkNanos(LockSupport.java:338)
at TimedWaitingState4$1.run(TimedWaitingState4.java:10)
Locked ownable synchronizers:
- None
方式 5：LockSupport.parkUntil(等待时间)
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.LockSupport;
public class TimedWaitingState5 {
public static void main(String[] args) throws InterruptedException {
Thread thread1 = new Thread(“thread1”) {
@Override
public void run() {
//等待500秒
LockSupport.parkUntil(System.currentTimeMillis() + TimeUnit.SECONDS.toMillis(500));
}
};
thread1.start();
//模拟休眠1秒，让thread1运行到parkNanos方法处
TimeUnit.SECONDS.sleep(1);
System.out.println(“thread1.state:” + thread1.getState());
}
}
输出
thread1.state:TIMED_WAITING
线程 thread1 堆栈信息
“thread1” #12 prio=5 os_prio=0 tid=0x00000000291b2000 nid=0x3cc0 waiting on condition [0x0000000029b8f000]
java.lang.Thread.State: TIMED_WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
at java.util.concurrent.locks.LockSupport.parkUntil(LockSupport.java:372)
at TimedWaitingState5$1.run(TimedWaitingState5.java:10)
Locked ownable synchronizers:
- None
2.6、状态 6：TERMINATED
执行完了 run()方法。其实这只是 Java 语言级别的一种状态，在操作系统内部可能已经注销了相应的线程，或者将它复用给其他需要使用线程的请求，而在 Java 语言级别只是通过 Java 代码看到的线程状态而已。
import java.util.concurrent.TimeUnit;
public class TerminatedState {
public static void main(String[] args) throws InterruptedException {
Thread thread1 = new Thread(“thread1”) {
@Override
public void run() {
System.out.println(Thread.currentThread());
}
};
thread1.start();
//休眠1秒，等待thread1执行完毕
TimeUnit.SECONDS.sleep(1);
System.out.println(“thread1 state:” + thread1.getState());
}
}
输出
Thread[thread1,5,main]
thread1 state:TERMINATED
3、状态转换图
这个图是本文的重点，反复看，消化理解！！！
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