[转]多线程任务分配实例

[url]http://www.iteye.com/problems/100706
[/url]

package com.lj.thread;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;

public class BasicTest
{
	
	public static void main(String[] args) throws InterruptedException, ExecutionException
	{
		List<String>list=new ArrayList<String>();
		
		for(int i=0;i<100;i++){
			list.add(i+",");
		}
		
		System.out.println(new BasicTest().list2Str(list, 5));
	}
	
	
	public String list2Str(List<String>list,final int nThreads) throws InterruptedException, ExecutionException{
		if(list==null||list.isEmpty()){
			return null;
			
		}
		
		
		StringBuffer ret=new StringBuffer();
		
		int size=list.size();
		
		ExecutorService executorService=Executors.newFixedThreadPool(nThreads);
		
		List<Future<String>> futures=new ArrayList<Future<String>>();
		
		for(int i=0;i<nThreads;i++){
			final List<String> subList=list.subList(size/nThreads*i, size/nThreads*(i+1));
			Callable<String>task=new Callable<String>(){

				@Override
				public String call() throws Exception
				{
					StringBuffer sb=new StringBuffer();
					for(String str:subList){
						sb.append(str);
					}
					
					return sb.toString();
				}
				
			};
			
			futures.add(executorService.submit(task));
		}
		
		
		for(Future<String>future:futures){
			System.out.println("Future<String>future:futures");
			ret.append(future.get());
		}
		
		executorService.shutdown();
		
		return ret.toString();
		
	}
}

这里Future<String>里的String就是返回类型。

可以改成任意其他类型如Future<List<Object>>






================================================

2014-07-21 更新：

package com.lj.socket;

import java.util.ArrayList;
import java.util.List;

public class Test02
{
	public static void main(String[] args)
	{
		List<String> all = new ArrayList<String>();
		all.add("h");
		all.add("w");
		all.add("c");
		all.add("2");
		all.add("x");

		int nthread = 2;

		System.out.println(all.size());
		int size = all.size();
 

		for (int i = 0; i < nthread; i++)
		{
			System.out.println(i);
			if (i + 1 == nthread)
			{
				System.out.println("hello");
				List<String> lastSub=all.subList(size/nthread*i, all.size());
				System.out.println("lastSub="+lastSub);
			} else
			{
				List<String> sub = all.subList(size / nthread * i, size / nthread * (i + 1));
				System.out.println("sub=" + sub);
			}
		}

	}
}

这个程序有个问题，就是最后一个sublist可能会无法包含到最终的数据。
而上面的代码修复了这个问题。