一、Java 線程的狀態(tài)
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java.lang.Thread.State
public enum State {
/**
* Thread state for a thread which has not yet started.
*/
NEW,
/**
* 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.
*/
RUNNABLE,
/**
* 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
* {@link Object#wait() Object.wait}.
*/
BLOCKED,
/**
* Thread state for a waiting thread.
* A thread is in the waiting state due to calling one of the
* following methods:
* <ul>
* <li>{@link Object#wait() Object.wait} with no timeout</li>
* <li>{@link #join() Thread.join} with no timeout</li>
* <li>{@link LockSupport#park() LockSupport.park}</li>
* </ul>
*
* <p>A thread in the waiting state is waiting for another thread to
* perform a particular action.
*
* For example, a thread that has called <tt>Object.wait()</tt>
* on an object is waiting for another thread to call
* <tt>Object.notify()</tt> or <tt>Object.notifyAll()</tt> on
* that object. A thread that has called <tt>Thread.join()</tt>
* is waiting for a specified thread to terminate.
*/
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:
* <ul>
* <li>{@link #sleep Thread.sleep}</li>
* <li>{@link Object#wait(long) Object.wait} with timeout</li>
* <li>{@link #join(long) Thread.join} with timeout</li>
* <li>{@link LockSupport#parkNanos LockSupport.parkNanos}</li>
* <li>{@link LockSupport#parkUntil LockSupport.parkUntil}</li>
* </ul>
*/
TIMED_WAITING,
/**
* Thread state for a terminated thread.
* The thread has completed execution.
*/
TERMINATED;
}
二、Java 線程狀態(tài)變遷
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簡單的理解:
- 當(dāng)線程執(zhí)行
wait()方法之后, 線程進入WAITING狀態(tài). - 進入等待狀態(tài)的線程需要依靠其他線程的通知才能夠返回到
RUNNABLE狀態(tài). -
TIME_WAITING狀態(tài)相當(dāng)于在WAITING狀態(tài)的基礎(chǔ)上增加了超時限制, 比如通過sleep(long millis)方法或wait(long millis)方法可以將Java線程置于TIME_WAITING狀態(tài). - 當(dāng)超時時間到達后
Java線程將會返回到RUNNABLE狀態(tài). - 當(dāng)線程調(diào)用
synchronized同步方法時, 在沒有獲取到鎖的情況下, 線程將會進入到BLOCKED狀態(tài). - 線程執(zhí)行完之后, 進入到
TERMINATED狀態(tài).
