七、并发容器ConcurrentHashMap

import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.CountDownLatch;

public class ConcurrentHashMapDemo {

    public static ConcurrentHashMap<String, String> concurrentHashMap = new ConcurrentHashMap<>();

    public static void main(String[] args) throws InterruptedException {
        CountDownLatch latch = new CountDownLatch(1);
        for (int i = 0; i < 10; i++) {
            new Thread(() -> {
                try {
                    latch.await();
                    concurrentHashMap.putIfAbsent("threadName", Thread.currentThread().getName());
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.println(Thread.currentThread().getName());
            }).start();
        }
        // 让子线程都等待
        Thread.sleep(10);
        // 并发执行
        latch.countDown();
        // 让子线程执行完毕
        Thread.sleep(1000);
        System.out.println(concurrentHashMap);
        System.out.println("finished");
    }
}