我正在做一些测试以了解 java 中的不同线程状态,并且遇到了一些查询。
通常,当一个线程被实例化时,它被称为处于 "NEW"
状态,然后当调用它的 start
() 方法时,操作系统调度程序获得控制权并处于 "RUNNABLE"
状态,当 run()
被 start()
内部调用时,它被称为处于运行状态。
Thread.currentThread().getState() // Returns the state of the thread
但是在执行下面的代码时观察到,即使在 run
方法中进行测试,线程状态也永远不会显示为 "RUNNING"
。
谁能帮我理解为什么它会这样?
public static void main(String[] args) {
System.out.println("Hello World");
Thread t=new Thread(()->{
System.out.println("Hi");
System.out.println(Thread.currentThread().getState()); //// STATE DISPLAYED AS "RUNNABLE" AGAIN
});
System.out.println(t.getState()); // STATE DISPLAYED AS "NEW"
t.start();
System.out.println(t.getState()); // STATE DISPLAYED AS "RUNNABLE"
}
lambda 表达式用于实现 run()
方法,我们在其中测试线程的状态,它再次显示为“RUNNABLE”而不是“RUNNING”
最佳答案
因为状态 RUNNING
不存在。如果您查看 getState
方法的定义,您会看到以下内容:
public State getState() {
// get current thread state
return jdk.internal.misc.VM.toThreadState(threadStatus);
}
如果你分析什么是State
,你会发现它是下面的ENUM:
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 {@code Object.wait()}
* on an object is waiting for another thread to call
* {@code Object.notify()} or {@code Object.notifyAll()} on
* that object. A thread that has called {@code Thread.join()}
* 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;
}
或来自 API Thread.State :
public static enum Thread.State extends Enum<Thread.State> A thread state. A thread can be in one of the following states:
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. A thread can be in only one state at a given point in time. These states are virtual machine states which do not reflect any operating system thread states.
关于java - run 方法内部的线程状态冲突;为什么线程状态不是 "RUNNING",我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/65467785/