java线程的状态到底是什么意思？答案

【问题标题】：What does the java thread's state really mean?java线程的状态到底是什么意思？
【发布时间】：2017-03-08 06:35:12
【问题描述】：

我在Android Studio学习工具，获取thread dump，如下：

我注意到这样的每个线程的不同状态，

我可以看到有runnable,sleeping,waiting。而我深入线程栈，大部分线程栈都是这样的，

"<61> RxComputationScheduler-3@830064517520" daemon prio=5 waiting
    java.lang.Thread.State: WAITING
        at java.lang.Object.wait(Object.java:-1)
        at java.lang.Thread.parkFor(Thread.java:1205)
        at sun.misc.Unsafe.park(Unsafe.java:325)
        at java.util.concurrent.locks.LockSupport.park(LockSupport.java:157)
        at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2017)
        at java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:1050)
        at java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:778)
        at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1035)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1097)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
        at java.lang.Thread.run(Thread.java:841)

我很困惑他们都停在Object.wait，但是线程的状态可以是runnable,sleeping,waiting?

这是另一个状态线程的堆栈。

RUNNABLE

<53> RxSchedulerPurge-1@830057651944" daemon prio=5 runnable
  java.lang.Thread.State: RUNNABLE
      at java.lang.Object.wait(Object.java:-1)
      at java.lang.Thread.parkFor(Thread.java:1205)
      at sun.misc.Unsafe.park(Unsafe.java:325)
      at java.util.concurrent.locks.LockSupport.parkNanos(LockSupport.java:197)
      at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.awaitNanos(AbstractQueuedSynchronizer.java:2056)
      at java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:1062)
      at java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:778)
      at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1035)
      at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1097)
      at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
      at java.lang.Thread.run(Thread.java:841)</code>

TIMED_WAITING

<58> RxScheduledExecutorPool-2@830064740632" daemon prio=5 sleeping
  java.lang.Thread.State: TIMED_WAITING
      at java.lang.Object.wait(Object.java:-1)
      at java.lang.Thread.parkFor(Thread.java:1205)
      at sun.misc.Unsafe.park(Unsafe.java:325)
      at java.util.concurrent.locks.LockSupport.parkNanos(LockSupport.java:197)
      at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.awaitNanos(AbstractQueuedSynchronizer.java:2056)
      at java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:1062)
      at java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:778)
      at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1035)
      at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1097)
      at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
      at java.lang.Thread.run(Thread.java:841)

【问题讨论】：

请使用code 代替图像进行堆栈跟踪。
请开始接受答案。我不是特别在谈论这个问题，我是在谈论所有你有好的但未被接受的答案的问题。

标签： java android performance thread-dump thread-state

【解决方案1】：

New表示如果您创建Thread类的实例但在调用start()方法之前线程处于新状态：

Thread t = new Thread(...); // t is New

Runnable表示调用start()方法后线程处于可运行状态。基本上：

t.start(); // t is Runnable

Running 是 Runnable 的“子状态”：如果线程调度程序选择了线程，则线程处于运行状态。你不能明确地用它做任何事情，这意味着你打电话给start()，然后等待。

Ready 是 Runnable 的另一个“子状态”：线程有资格运行并等待线程调度程序选择它。

Blocked 表示线程仍处于活动状态，但当前没有资格运行时的状态。例如，当一个线程遇到由另一个线程处理的synchronized 块时，就会发生这种情况。在这种情况下，第一个线程变为阻塞。

Waiting 是您的线程既没有阻塞也没有准备好的状态。这通常发生在您在线程上调用 wait() 或 join() 时。

Thread t1 = new Thread(); // t1 is New
Thread t2 = new Thread(); // t2 is New
t1.start(); // t1 becomes Runnable
t2.start(); // t2 becomes Runnable
t1.join(); // t2 becomes Waiting, because t1 is processed until it terminates

还有一种状态叫Timed Waiting，几乎是一样的东西，只不过是调用sleep()引起的。如果调用wait(timeout) 或join(timeout)，线程也会进入定时等待状态。

Thread t = new Thread(); // t is New
t.start(); // t is Runnable
t.sleep(4000); // t get state of Timed Waiting for 4 seconds

Terminated是一个线程在run()方法退出时处于终止或死亡状态。

我想我已经涵盖了所有内容：）这是一张可以帮助您更清楚地理解它的图片：

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这只是一个良好的谷歌搜索技巧问题，真的......

【讨论】：

能否请您发布您的来源以及您从哪里获取此信息？

【解决方案2】：

public static enum Thread.State
extends Enum<Thread.State>

线程状态。线程可以处于以下状态之一：

NEW
A thread that has not yet started is in this state.

RUNNABLE
A thread executing in the Java virtual machine is in this state.

BLOCKED
A thread that is blocked waiting for a monitor lock is in this state.

WAITING
A thread that is waiting indefinitely for another thread to perform a particular action is in this state.

TIMED_WAITING
A thread that is waiting for another thread to perform an action for up to a specified waiting time is in this state.

TERMINATED
A thread that has exited is in this state.

一个线程在给定的时间点只能处于一种状态。这些状态是不反映任何操作系统线程状态的虚拟机状态。

请参阅oracle's api 了解更多信息。

【讨论】：