通过例子理解wait和notify 1.notify后wait的线程无法立刻唤醒 2.要等到notify的线程退出sunchronized后才行

Data.java

package org.example.testwaitnotify;

public class Data {
    private int value;

    public int getValue() {
        return value;
    }

    public void setValue(int value) {
        this.value = value;
    }
}

ThreadA.java

package org.example.testwaitnotify;

import java.util.concurrent.TimeUnit;

public class ThreadA extends Thread {
    private Data data;

    private Object lock;

    public ThreadA(Data data, Object lock) {
        this.data = data;
        this.lock = lock;
    }

    @Override
    public void run() {
        System.out.println("A start");
        synchronized (lock) {
            System.out.println("A Enter");
            try {
                TimeUnit.SECONDS.sleep(2);
                data.setValue(666);
                lock.notify();
                TimeUnit.SECONDS.sleep(10);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}

Main.java

package org.example.testwaitnotify;

public class Main {
    public static void main(String[] args) {
        Data data = new Data();
        Object lock = new Object();
        new ThreadA(data, lock).start();

        System.out.println("Main start");
        synchronized (lock) {
            try {
                lock.wait();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println("Main read val=" + data.getValue());
        }
    }
}

理解：

在Main等着的时候，ThreadA即使notify了，只是说：Main处于就绪状态了，依然无法立刻获得锁。

依然要等到ThreadA执行完，退出synchronized后，才会释放锁，Main才会获得锁接着执行。

思考：

wait后是线程进入WAITING状态。 别的线程notify它后，应该是进入等待被cpu调度的状态，不知道为什么6个 状态没这个状态？(NEW、RUNNABLE、BLOCKED、WAITING、TIMED_WAITING、TERMINATED)