CountDownLatch 使用示例

向右看齐 2022-04-06 06:40 193阅读 0赞

简单介绍下使用CountDownLatch 的使用方法  
CountDownLatch 是在开始指定线程数，然后通过 latch.countDown();终止一次线程数-1，最后执行完成通过  
调用 latch.await(); 在这个方法之后，所有的线程都执行完毕。  
我的使用场景是异步的数据组装。

下面贴出一些简单的实例代码，基于此代码可以参考 CountDownLatch 的使用

package com.example.thread;
    
    import java.util.List;
    import java.util.concurrent.CountDownLatch;
    
    /** * 类BuildBaseInfoThread.java的实现描述：TODO 类实现描述 * * @author xupeng 2017年5月15日 下午6:58:01 */
    public class BuildBaseInfoThread extends Thread { 
    
        private CountDownLatch latch;
        private List<String>   result;
    
        @Override
        public void run() {
            try {
                Thread.sleep(1000);
                result.add("baseInfo");
    
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                latch.countDown();
                System.out.println(latch.getCount());
            }
        }
    
        public BuildBaseInfoThread(CountDownLatch latch, List<String> result) {
            super();
            this.latch = latch;
            this.result = result;
        }
    }

package com.example.thread;
    
    import java.util.ArrayList;
    import java.util.List;
    import java.util.concurrent.CountDownLatch;
    
    /** * 类BuildBaseInfoThread.java的实现描述：TODO 类实现描述 * * @author xupeng 2017年5月15日 下午6:58:01 */
    public class BuildExtendInfoThread extends Thread { 
    
        private CountDownLatch latch;
        private List<String>   result;
    
        @Override
        public void run() {
            try {
                Thread.sleep(2000);
                List<String> list = new ArrayList<String>();
    // synchronized (result) {同步汇总
    // result.addAll(list);
    // }
                result.add("extend");
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                }
                latch.countDown();
                System.out.println(latch.getCount());
            }
        }
    
        public BuildExtendInfoThread(CountDownLatch latch, List<String> result) {
            super();
            this.latch = latch;
            this.result = result;
        }
    }

package com.example.thread;
    
    import java.util.ArrayList;
    import java.util.List;
    import java.util.concurrent.CountDownLatch;
    
    public class CountDownLatchTest {
    
        public static void main(String[] args) {
            CountDownLatch latch = new CountDownLatch(2);
            List<String> result = new ArrayList<String>();
    
            new BuildBaseInfoThread(latch, result).start();
    
            new BuildExtendInfoThread(latch, result).start();
    
            System.out.println(result);
            try {
                latch.await();
    
                System.out.println(result);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
    
        }
    }