java 多线程 CountDownLatch用法

墨蓝 2021-09-20 02:26 370阅读 0赞

[为什么80%的码农都做不了架构师？>>> ][80_]  ![hot3.png][]

CountDownLatch，一个同步辅助类，在完成一组正在其他线程中执行的操作之前，它允许一个或多个线程一直等待。

主要方法

public CountDownLatch(int count);

public void **countDown**();

public void **await**() throws [InterruptedException][]

构造方法参数指定了计数的次数

countDown方法，当前线程调用此方法，则计数减一

awaint方法，调用此方法会一直阻塞当前线程，直到计时器的值为0

private List<EventSignToSmallDto> getEventSignToSmallDtoList(Long eventId, String source) throws Exception {
            //所有报名数据
            List<EventSignSPVo> signUserList = eventSignDao.listByArgs(eventId, source, null, null);
            // 存储用户信息
            final ConcurrentMap<Long, EventUserBaseInfo> users = new ConcurrentHashMap<Long, EventUserBaseInfo>();
    
            if (signUserList != null && signUserList.size() > 0) {
                int unit = 50;
                int size = signUserList.size();
                // 线程数量
                int count = (size / unit) + (size % unit > 0 ? 1 : 0);
                // 线程计数器
                final CountDownLatch countDownLatch = new CountDownLatch(count);
                // 线程池
                ExecutorService exec = Executors.newFixedThreadPool(count);
                // 查询字段定义
                final UserField[] userFields = new UserField[]{UserField.USER_ID, UserField.NAME, UserField.COMPANY,
                        UserField.POSITION, UserField.PROVINCE, UserField.CITY, UserField.TYPE, UserField.MOBILE,
                        UserField.ZHISLAND_TYPE, UserField.TURNOVER, UserField.INDUSTRY, UserField.COUNTRY_CODE_SHOW,
                        UserField.ACTIVITY, UserField.END_TIME};
    
                for (int i = 0; i < count; i++) {
                    final StringBuilder stringBuilder = new StringBuilder();
                    for (int x = i * unit; x < (i + 1) * unit; x++) {
                        stringBuilder.append(signUserList.get(x).getUserId()).append(",");
                        if (x + 1 >= size) {
                            break;
                        }
                    }
                    // 获取用户基础信息
                    Runnable getBaseInfo = new Runnable() {
                        public void run() {
                            try {
                                Map<Long, EventUserBaseInfo> temp = getBaseInfo(userFields,
                                        stringBuilder.substring(0, stringBuilder.length() - 1));
                                if (temp != null) {
                                    users.putAll(temp);
                                }
                            } catch (Exception e) {
                                logger.error("查询用户信息出错！", e);
                            } finally {
                                // 任务执行完成后，数量减一
                                countDownLatch.countDown();
                            }
                        }
                    };
                    exec.submit(getBaseInfo);
                }
                countDownLatch.await();
                exec.shutdown();
            }
            //用户数据获取完毕
    
            return buildWorkbook(signUserList, users);
        }

转载于:https://my.oschina.net/luanwu/blog/1589178

[80_]: https://my.oschina.net/u/2663968/blog/3051541
[hot3.png]: /images/20210726/84557c815f224e589a688a50b672bc9f.png
[InterruptedException]: http://www.iteye.com/java/lang/InterruptedException.html