ThreadLocal

import org.junit.Test;

import java.util.concurrent.CountDownLatch;

public class ThreadTest {
    @Test
    public void testInit() {
        for (int i = 0; i < 10; i++) {
            ThreadInfo info = new ThreadInfo();
            info.set(true);
        }
    }

    @Test
    public void testThread() throws InterruptedException {
        int max = 5;
        final CountDownLatch countDownLatch = new CountDownLatch(max);
        for (int i = 0; i < max; i++) {
            new Thread() {
                @Override
                public void run() {
                    for (int j = 0; j < 10; j++) {
                        ThreadInfo info = new ThreadInfo();
                        info.set(true);
                    }
                    countDownLatch.countDown();
                }
            }.start();
        }
        countDownLatch.await();
    }
}

class ThreadInfo {
    private static ThreadLocal<Boolean> test = new ThreadLocal<Boolean>() {
        @Override
        protected Boolean initialValue() {
            System.out.println(Thread.currentThread().getId() + " init false");
            return false;
        }
    };

    public void set(boolean value) {
        if (test.get() != value) {
            System.out.println(Thread.currentThread().getId() + " change " + test.get() + " -> " + value);
        }
        test.set(value);
    }
}