Java中怎么实现线程状态的切换

    // Note that this method should not return until AFTER all threads have died.
    public void close() throws IOException {

        // Copy to avoid concurrent modification problems.
        List copy = null;
        synchronized (workersLock) {
            copy = new ArrayList<>(workers);
        }

        for (WorkerThread wt : copy) {
            wt.close();
            while (wt.getState() != Thread.State.TERMINATED) {
                try {
                    wt.join();
                } catch (InterruptedException exc) {
                    wrapper.interruptedJoinCallWhileClosingThreadPool(exc, wt, this);
                }
            }
        }

        threadGroup = null;
    }

/**
 * @program: learning
 * @description: 用于确认线程状态问题
 * @author: Jarry
 * @create: 2020-10-26 22:25
 **/
public class ThreadState {

    public static void main(String[] args) {
        threadStateTest();
//        threadStateTest2();
//        threadStateWithBlocked();
//        threadStateWithException();
//        threadStateWithSuspend();
    }

    /**
     * 实践证明：Thread.suspend()与Thread.resume()不会改变线程状态
     * 线程状态该是Waiting，就Waiting。该Timed_Waiting就Timed_Waiting
     * Thread.suspend()与Thread.resume()只是挂起目标线程（并且不会释放锁资源）
     */
    private static void threadStateWithSuspend() {
        Thread thread1 = new Thread(() -> {
//            LockSupport.park();
            LockSupport.parkNanos(2000000000);
        });

        thread1.start();
        printThreadState(thread1);
        LockSupport.parkNanos(500000000);
        printThreadState(thread1);
        thread1.suspend();
        printThreadState(thread1);
        LockSupport.parkNanos(500000000);
        printThreadState(thread1);
        thread1.resume();
        LockSupport.parkNanos(500000000);
        printThreadState(thread1);

//        LockSupport.unpark(thread1);
    }

    /**
     * 展现线程阻塞状态
     */
    private static void threadStateWithBlocked() {
        Runnable runnable = new Runnable() {
            @Override
            public void run() {
                synchronized (ThreadState.class) {
//                    LockSupport.parkNanos(2000000000);
                    LockSupport.park();
                }
            }
        };

        Thread thread1 = new Thread(runnable);
        Thread thread2 = new Thread(runnable);

        thread1.start();
        LockSupport.parkNanos(500000000);
        thread2.start();
        // 加上以下时间间隔，则结果：Runnable->Blocked
        // 推论：Thread.start()会将线程状态设置为Runnable，然后在遇到sync的锁，再切换为Blocked状态
//        LockSupport.parkNanos(500000000);

        printThreadState(thread2);
        LockSupport.parkNanos(500000000);
        printThreadState(thread2);

        LockSupport.parkNanos(500000000);
        LockSupport.unpark(thread1);
        LockSupport.unpark(thread2);

    }

    /**
     * 由于底层实现机制的不同（相较于其他waiting的方法），无法直接进行Object.wait()，否则会抛出以下异常
     * @exception java.lang.IllegalMonitorStateException
     * object.wait()进行wait的方法，是直接对其wait_set进行操作
     */
    private static void threadStateWithException() {
        Thread thread1 = new Thread(() -> {
            try {
                ThreadState.class.wait(2000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }

        });

        thread1.start();
        LockSupport.parkNanos(1000000000);
        printThreadState(thread1);

    }

    /**
     * Object.wait()的使用
     */
    private static void threadStateTest3() {
        Thread thread1 = new Thread(() -> {
            synchronized (ThreadState.class) {
                try {
                    ThreadState.class.wait(2000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        });

        thread1.start();
        LockSupport.parkNanos(1000000000);
        printThreadState(thread1);

    }

    /**
     * 确定LockSupport.parkNacos()是否可以生成Time_Waiting状态
     */
    private static void threadStateTest2() {
        Thread thread1 = new Thread(() -> {
            LockSupport.parkNanos(2000000000);
        });

        thread1.start();
        printThreadState(thread1);
        LockSupport.parkNanos(1000000000);

        printThreadState(thread1);
    }

    /**
     * 查看到除Blocked以外的所有线程状态
     */
    private static void threadStateTest() {
        Thread thread1 = new Thread(() -> {
            synchronized (ThreadState.class) {
                // Runnable
                printThreadState(Thread.currentThread());

                // 1.Thread.sleep(time)
            try {
                Thread.sleep(2000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
                // 2.Object.wait(time)
//                try {
//                    ThreadState.class.wait(2000);
//                } catch (InterruptedException e) {
//                    e.printStackTrace();
//                }
                // 3.Thread.join(time)
//                try {
//                    Thread.currentThread().join(2000);
//                } catch (InterruptedException e) {
//                    e.printStackTrace();
//                }
                // 4.LockSupport.parkNanos(time);
//            LockSupport.parkNanos(2000000000);
                // 5.LockSupport.parkUntil(timeStamp);
//            LockSupport.parkUntil(System.currentTimeMillis()+2000);

                LockSupport.park();
            }

        });
        thread1.setName("test_thread");

        // New
        printThreadState(thread1);

        thread1.start();
        LockSupport.parkNanos(1000000000);
        // Timed_waiting
        printThreadState(thread1);

        LockSupport.parkNanos(2000000000);
        // Waiting
        printThreadState(thread1);

        LockSupport.unpark(thread1);

        LockSupport.parkNanos(1000000000);
        // Terminated
        printThreadState(thread1);


    }

    private static void printThreadState(Thread thread) {
        System.out.println("current Thread(" + thread.getName()+":" + thread.getId() + ") state:" + thread.getState());
    }

}