Java LockSupport常用方法的源码分析

    // Hotspot implementation via intrinsics API
    private static final sun.misc.Unsafe UNSAFE;
    private static final long parkBlockerOffset;
    private static final long SEED;
    private static final long PROBE;
    private static final long SECONDARY;
    static {
        try {
            UNSAFE = sun.misc.Unsafe.getUnsafe();
            Class<?> tk = Thread.class;
            parkBlockerOffset = UNSAFE.objectFieldOffset
                (tk.getDeclaredField("parkBlocker"));
            SEED = UNSAFE.objectFieldOffset
                (tk.getDeclaredField("threadLocalRandomSeed"));
            PROBE = UNSAFE.objectFieldOffset
                (tk.getDeclaredField("threadLocalRandomProbe"));
            SECONDARY = UNSAFE.objectFieldOffset
                (tk.getDeclaredField("threadLocalRandomSecondarySeed"));
        } catch (Exception ex) { throw new Error(ex); }
    }

    public static void park(Object blocker) {
        Thread t = Thread.currentThread();
        setBlocker(t, blocker);
        UNSAFE.park(false, 0L);
        setBlocker(t, null);
    }
    private static void setBlocker(Thread t, Object arg) {
        // Even though volatile, hotspot doesn't need a write barrier here.
        UNSAFE.putObject(t, parkBlockerOffset, arg);
    }

    public static void park(Object blocker) {
        Thread t = Thread.currentThread();
        setBlocker(t, blocker);
        UNSAFE.park(false, 0L);
        setBlocker(t, null);
    }

    public static void parkUntil(Object blocker, long deadline) {
        Thread t = Thread.currentThread();
        setBlocker(t, blocker);
        UNSAFE.park(true, deadline);
        setBlocker(t, null);
    }

    public static void parkNanos(Object blocker, long nanos) {
        if (nanos > 0) {
            Thread t = Thread.currentThread();
            setBlocker(t, blocker);
            UNSAFE.park(false, nanos);
            setBlocker(t, null);
        }
    }

    public static void unpark(Thread thread) {
        if (thread != null)
            UNSAFE.unpark(thread);
    }

package XIAOWEI;
import java.util.concurrent.locks.LockSupport;

​​​​​​​public class Xiaowei{
    public static void main(String[] args) {
        Thread A = new Thread(()-> {
            System.out.println("线程A已经被阻塞QWQ");
            LockSupport.park();
            System.out.println("线程A被线程B唤醒啦~~~");
        });
        A.start();
        new Thread(()->{
            System.out.println("线程B在唤醒线程A ing~~~");
            LockSupport.unpark(A);
        },"B").start();
    }
}

package XIAOWEI;
import java.util.concurrent.locks.LockSupport;
public class Xiaowei {
    public static void main(String[] args) {
        Thread A = new Thread(()-> {
            try {
                Thread.sleep(2000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println("线程A已经被阻塞QWQ(第二版)");
            LockSupport.park();
            System.out.println("线程A被线程B唤醒啦~~~（第二版）");
        });
        A.start();
        new Thread(()->{
            System.out.println("线程B在唤醒线程A ing~~~驾驾驾");
            LockSupport.unpark(A);
        },"B").start();
    }
}