主线程等待次线程执-优快云博客

本文介绍了一个简单的线程计数实现方案，通过自定义`MyCountDown`类来同步跟踪并减少活跃线程数量，确保所有任务完成。同时展示了如何通过`ImportThread`类创建多个线程，并在主线程中等待所有子线程执行完毕。

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一、

package com.shine.bill;

public class MyCountDown {

   private int count;

   public MyCountDown(int count) {
       this.count = count;
   }

   public synchronized void countDown() {
       count--;
   }

   public synchronized boolean hasNext() {
       return (count > 0);
   }

   public int getCount() {
       return count;
   }

   public void setCount(int count) {
       this.count = count;
   }

}

二、

package com.shine.bill;

public class ImportThread extends Thread {

   private MyCountDown c;

   public ImportThread(MyCountDown c) {
       this.c = c;
   }

   @Override
   public void run() {
       System.out.println(Thread.currentThread().getName() + "开始...");// 打印开始标记
       // Do something
       System.out.println(Thread.currentThread().getName() + "结束. 还有"
               + c.getCount() + " 个线程");// 打印结束标记

c.countDown();// 计时器减1
}

}

三、

package com.shine.bill;

public class Test2 {

   /**
   * @param args
   */
   public static void main(String[] args) {

       System.out.println(Thread.currentThread().getName() + "开始");// 打印开始标记
       int threadNum = 100;
       MyCountDown c = new MyCountDown(threadNum);// 初始化countDown
       for (int ii = 0; ii < threadNum; ii++) {// 开threadNum个线程
           Thread t = new ImportThread(c);
           t.start();
       }
       while (true) {// 等待所有子线程执行完
           if (!c.hasNext())
               break;
       }
       System.out.println(Thread.currentThread().getName() + "结束.");// 打印结束标
   }

}

四、分机部署

    public static void main(String[] args) {

       Long marchineNum = 3L;
       Long totalCount=10L;
       for (int i = 1; i <= marchineNum; i++) {
           // 从第几条记录开始
           long startIndex = (i - 1) *(totalCount/marchineNum);
           long endIndex=0;
           // 从第几条记录结束
           if(i==marchineNum)
           {
               endIndex =10L-1;
           }else{
               endIndex = startIndex + (totalCount/marchineNum)-1;
           }

           System.out.println("区间："+startIndex+"-"+endIndex);
       }

   }