java多线程（十四）八锁CopyOnWriteArrayListCopyOnWriteArraySetConcurrentHashMapCallable

Posted 2021-07-07 500年

1、八锁

1、同一把锁时，谁先拿到，谁执行；
2、new this 锁为具体的对象；
3、static 锁为Class唯一的一个模板；

2、CopyOnWriteArrayList

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Vector;
import java.util.concurrent.CopyOnWriteArrayList;

public class CopyOnWriteArrayListDemo {

	public static void main(String[] args) {
		// List<String> list = new ArrayList<String>();// 线程不安全
		// List<String> list = new Vector<>();
		// List<String> list = Collections.synchronizedList(new ArrayList<>());
		List<String> list = new CopyOnWriteArrayList<>();

		for (int i = 0; i < 10; i++) {
			new Thread(() -> {
				list.add(Thread.currentThread().getName());
				System.out.println(list);
			}, String.valueOf(i)).start();
		}
	}
}

3、CopyOnWriteArraySet

import java.util.Collections;
import java.util.HashSet;
import java.util.Set;
import java.util.concurrent.CopyOnWriteArraySet;

public class CopyOnWriteArraySetDemo {

	public static void main(String[] args) {
		// Set<String> set = new HashSet<String>();// 不安全
		// Set<String> set = Collections.synchronizedSet(new HashSet<>());
		Set<String> set = new CopyOnWriteArraySet<String>();

		for (int i = 0; i < 10; i++) {
			new Thread(() -> {
				set.add(Thread.currentThread().getName());
				System.out.println(set);
			}, String.valueOf(i)).start();
		}
	}

}

4、ConcurrentHashMap

import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

public class ConcurrentHashMapDemo {

	public static void main(String[] args) {
		// Map<String, String> map = new HashMap<String, String>();// 多线程-不安全
		Map<String, String> map = new ConcurrentHashMap<>();

		for (int i = 0; i < 10; i++) {
			new Thread(() -> {
				map.put(Thread.currentThread().getName(), Thread.currentThread().getName());
				System.out.println(map);
			}, String.valueOf(i)).start();
		}
	}

}

5、Callable

import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.FutureTask;

public class CallableTest {

	public static void main(String[] args) throws InterruptedException, ExecutionException {

		FutureTask<String> futureTask = new FutureTask<>(new MyCallable());
		
		new Thread(futureTask).start();
		new Thread(futureTask).start();
		String string = futureTask.get();// 此处可能会产生阻塞
		System.out.println(string);
	}

}

class MyCallable implements Callable<String> {

	@Override
	public String call() throws Exception {
		System.out.println("call");
		return "hao";
	}

}

特别鸣谢：狂神说Java老师的无私奉献

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