CompletionService计算1-1000000000的和

package com.example.wxh.queue;

import java.util.concurrent.Callable;
import java.util.concurrent.CompletionService;
import java.util.concurrent.ExecutorCompletionService;
import java.util.concurrent.Future;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;

/**

• Created by
• 通用的多线程，算分页的逻辑 ，计算一推数据，算出分页再多线程处理
• @auth wangxinhui
• @Date 2019/11/29
  */
  public class CommonCompletion {

public static void main(String args[]){
    long starttime = System.currentTimeMillis();
    int totals = 1000000000;

    int coreThread = 5;
    int nThread = 20;
    LinkedBlockingQueue linkedBlockingQueue = new LinkedBlockingQueue(10);  //阻塞队列
    ThreadPoolExecutor poolExecutor =  new ThreadPoolExecutor(coreThread, nThread,
            0L, TimeUnit.MILLISECONDS,
            linkedBlockingQueue);

    LinkedBlockingQueue> QueueingFuture = new LinkedBlockingQueue>(10);
    CompletionService completionService = new ExecutorCompletionService(poolExecutor,QueueingFuture);

    long step = totals/nThread;  //每页处理的条数 ： pageSize

    for(int i=1;i<= nThread ;i++){
        long start = (i-1)*step+1;   //开启的条数
        long end;
        if (i==nThread){ //是否是最后一个线程
            end = totals;
        }else{
            end = i*step;
        }
        completionService.submit(new Callable() {
            long result = 0l;
            @Override
            public Long call() throws Exception {
                for(long i= start ;i<= end;i++){
                    result+=i;
                }
                System.out.println(Thread.currentThread() +"--"+ poolExecutor.toString() +"------"+start + "~"+ end+",result =" +result);
                return  result;
            }
        });
    }

    long count = 0l;
    for(int i = 1 ; i<= nThread ; i++){
        try {
            count += completionService.take().get();
            System.out.println("i="+i+",count =" +count);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    System.out.println(" count= "+count);
    System.out.println(" task done !");
    System.out.println(" times ="+(System.currentTimeMillis()-starttime));
    poolExecutor.shutdown();
}

}