java并发---线程不安全类及其同步容器

平时中我们使用的很多类都是线程不安全的，那么下面给出线程不安全的类及其对应的同步容器。

同步容器只是加了锁，并不代表并发安全，一般项目不推荐使用。

ArrayList------------------------->Vector, Stack

HashMap------------------------>HashTable

Collections.syncronizedXXX(List, Set, Map)

Collections.syncronizedXXX的实现方法如下：

package concurrency.example.syncContainer;

import concurrency.annotations.ThreadSafe;
import lombok.extern.slf4j.Slf4j;

import java.util.Collections;
import java.util.List;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Semaphore;

/*
 *Created by William on 2018/5/1 0001
 */
@Slf4j
@ThreadSafe
public class ListSafeCollectionsSync {

    public static int clientTotal = 5000;
    public static int threadTotal = 200;
    private static List<Integer> arrayList = Collections.synchronizedList(new ArrayList<>());

    public static void main(String[] args) throws InterruptedException {
        ExecutorService executorService = Executors.newCachedThreadPool();
        Semaphore semaphore = new Semaphore(threadTotal);
        CountDownLatch countDownLatch = new CountDownLatch(clientTotal);
        for (int i = 0; i < clientTotal; i++) {
            final int finalI = i;
            executorService.execute(new Runnable() {
                @Override
                public void run() {
                    try {
                        semaphore.acquire();
                        update(finalI);
                        semaphore.release();
                    } catch (Exception e) {
                        log.error("Exception", e);
                    }
                    countDownLatch.countDown();
                }
            });
        }
        countDownLatch.await();
        executorService.shutdown();
        log.info("size:{}",arrayList.size());
    }

    public static void update(int i) {
        arrayList.add(i);
    }

输出结果为5000，线程安全。