java的线程，实现线程状态
在Java中，要获取线程的当前状态，请使用Thread.getState（）方法获取线程的当前状态。Java提供了java.lang.Thread.State类，它定义了线程状态的ENUM常量，如下所示：
常量类型：NEW
声明：public static final Thread.State NEW
描述：尚未启动的线程的线程状态。
常量类型：Runnable
声明：public static final Thread.State RUNNABLE
描述：可运行线程的线程状态。处于可运行状态的线程正在Java虚拟机中执行，但它可能正在等待来自操作系统的其他资源，例如处理器。
常量类型：BLOCKED
声明：public static final Thread.State BLOCKED
描述：线程阻塞等待监视器锁定的线程状态。处于阻塞状态的线程正在等待监视器锁定以在调用Object.wait（）之后输入同步块/方法或重新输入同步块/方法。
常量类型：WAITING
声明：public static final Thread.State WAITING
描述：等待线程的线程状态。等待线程的线程状态。由于调用以下方法之一，线程处于等待状态：
Object.wait with no timeout
Thread.join with no timeout
LockSupport.park
处于等待状态的线程正在等待另一个线程执行特定操作。
常量类型：Time waiting
声明：public static final Thread.State TIMED_WAITING
描述：具有指定等待时间的等待线程的线程状态。由于在指定的正等待时间内调用以下方法之一，线程处于定时等待状态：
Thread.sleep
Object.wait with timeout
Thread.join with timeout
LockSupport.parkNanos
LockSupport.parkUntil
常量类型：Terminated
声明：public static final Thread.State TERMINATED
描述：已终止线程的线程状态。线程已完成执行。
// Java program to demonstrate thread states
class thread implements Runnable
{
public void run()
{
// moving thread2 to timed waiting state
try
{
Thread.sleep(1500);
}
catch (InterruptedException e)
{
e.printStackTrace();
}
try
{
Thread.sleep(1500);
}
catch (InterruptedException e)
{
e.printStackTrace();
}
System.out.println("State of thread1 while it called join() method on thread2 -"+
Test.thread1.getState());
try
{
Thread.sleep(200);
}
catch (InterruptedException e)
{
e.printStackTrace();
}
}
}
public class Test implements Runnable
{
public static Thread thread1;
public static Test obj;
public static void main(String[] args)
{
obj = new Test();
thread1 = new Thread(obj);
// thread1 created and is currently in the NEW state.
System.out.println("State of thread1 after creating it - " + thread1.getState());
thread1.start();
// thread1 moved to Runnable state
System.out.println("State of thread1 after calling .start() method on it - " +
thread1.getState());
}
public void run()
{
thread myThread = new thread();
Thread thread2 = new Thread(myThread);
// thread1 created and is currently in the NEW state.
System.out.println("State of thread2 after creating it - "+ thread2.getState());
thread2.start();
// thread2 moved to Runnable state
System.out.println("State of thread2 after calling .start() method on it - " +
thread2.getState());
// moving thread1 to timed waiting state
try
{
//moving thread2 to timed waiting state
Thread.sleep(200);
}
catch (InterruptedException e)
{
e.printStackTrace();
}
System.out.println("State of thread2 after calling .sleep() method on it - "+
thread2.getState() );
try
{
// waiting for thread2 to die
thread2.join();
}
catch (InterruptedException e)
{
e.printStackTrace();
}
System.out.println("State of thread2 when it has finished it's execution - " +
thread2.getState());
}
}
输出：
State of thread1 after creating it - NEW
State of thread1 after calling .start() method on it - RUNNABLE
State of thread2 after creating it - NEW
State of thread2 after calling .start() method on it - RUNNABLE
State of thread2 after calling .sleep() method on it - TIMED_WAITING
State of thread1 while it called join() method on thread2 -WAITING
State of thread2 when it has finished it's execution - TERMINATED
说明：创建新线程时，线程处于NEW状态。在线程上调用.start（）方法时，线程调度程序将其移动到Runnable状态。每当在线程实例上调用join（）方法时，执行该语句的当前线程将等待此线程移动到Terminated状态。因此，在控制台上打印最终语句之前，程序调用thread2上的join（），使thread1等待，而thread2完成其执行并移至Terminated状态。thread1进入等待状态，因为它等待thread2完成它的执行，因为它在thread2上调用了join。
