Java マルチスレッドの詳細な分析: スレッドの状態遷移とスレッド間通信を理解する

           |
           V
New -> Runnable -> Blocked -> Runnable -> Terminated
           |    ^        |
           V    |        |
        Waiting <-       |
           |    |
           V    |
   Timed Waiting <---

public class ThreadStateExample {
    public static void main(String[] args) throws Exception {
        Thread thread = new Thread(() -> {
            try {
                Thread.sleep(1000); // 线程进入Timed Waiting状态
                synchronized (ThreadStateExample.class) { // 线程进入Blocked状态
                    ThreadStateExample.class.wait(); // 线程进入Waiting状态
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        });
        System.out.println("Thread state: " + thread.getState()); // NEW
        thread.start();
        System.out.println("Thread state: " + thread.getState()); // RUNNABLE
        Thread.sleep(200); // 让线程有足够的时间进入Timed Waiting状态
        System.out.println("Thread state: " + thread.getState()); // TIMED_WAITING
        Thread.sleep(1000); // 让线程有足够的时间进入Waiting状态
        System.out.println("Thread state: " + thread.getState()); // WAITING
        synchronized (ThreadStateExample.class) {
            ThreadStateExample.class.notify(); // 唤醒线程
        }
        Thread.sleep(200);
        System.out.println("Thread state: " + thread.getState()); // BLOCKED
        thread.join();
        System.out.println("Thread state: " + thread.getState()); // TERMINATED
    }
}

public class ThreadCommunicationExample {
    static class SharedObject {
        private int value;
        private boolean isValueReady;

        public synchronized int getValue() {
            while (!isValueReady) {
                try {
                    wait(); // 等待value准备好
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
            return value;
        }

        public synchronized void setValue(int value) {
            this.value = value;
            isValueReady = true; // 设置value准备好的标记
            notify(); // 唤醒等待的线程
        }
    }

    public static void main(String[] args) {
        SharedObject sharedObject = new SharedObject();

        Thread readerThread = new Thread(() -> {
            int value = sharedObject.getValue();
            System.out.println("The value is: " + value);
        });

        Thread writerThread = new Thread(() -> {
            int value = 42;
            sharedObject.setValue(value);
        });

        readerThread.start();
        writerThread.start();
    }
}