有一个map，key存储候选人名称，value存储该候选人的得票数。请实现一个线程安全的投票系统.

为了测试并发环境下的表现，我们先设计一个小的“框架”，用来模拟并发情况下的投票行为。 首先设计一个接口，代测试的代码在这个接口的方法里面被调用

public interface Worker {    void doWork();}

然后是并发执行器

public class ConcurrentRunner {    private static   int  threadCount = 0;    private  Worker worker;    public void setWorker(Worker w){        worker = w;    }    private ExecutorService service = Executors.newCachedThreadPool();    ConcurrentRunner(int  count ){        threadCount = count;    }    private final CountDownLatch countDownLatch = new CountDownLatch(threadCount);    public void run(){        for (int i = 0; i < threadCount; i++) {            Runnable runnable = new Runnable() {                public void run() {                    try {                        countDownLatch.await();                        worker.doWork();                    } catch (Exception e) {                        e.printStackTrace();                    }                }            };            service.execute(runnable);             //达到threadcount线程数量的时候，所有线程以前执行            countDownLatch.countDown();        }    }}

下面进入正题，这个题目主要考察的是并发控制，当然你可以用整个方法都加锁来实现，但是效率低下，借鉴CAS的思想来实现是最优解决方案：

import java.util.HashMap;import java.util.Random;import java.util.concurrent.ConcurrentHashMap;/** * Created by yzy on 2018/10/31. */public class Main {    /**     * 投票人数量     */    public static final int VOTER_COUNT = 100;    /**     * 候选人数量     */    public static final int CANDINATE_COUNT = 3;    /**     * 候选人     * @param args     */    public static final String[]  candinator = {"tom","lily","jimmy"} ;  //  private static HashMap
    
      result = new HashMap(3);    private static  ConcurrentHashMap
     
       result = new ConcurrentHashMap(3);    public static void main(String[] args) {        ConcurrentRunner concurrentRunner = new ConcurrentRunner(VOTER_COUNT);        concurrentRunner.setWorker(new Worker() {            @Override            public void doWork() {                Random random = new Random();                int index = random.nextInt(3);                System.out.println("who="+index);                String who = candinator[index];             //   int num = result.get(who);             //   result.put(who,1);                result.putIfAbsent(who,0);                int num = 0;             //  while(!result.replace(who,num=result.get(who),num++)){             //   while(!result.replace(who,num=result.get(who),++num)){                while(!result.replace(who,num=result.get(who),num + 1)){                }            }        });        concurrentRunner.run();        System.out.println("tom 票数" + result.get("tom"));        System.out.println("lily 票数 " + result.get("lily"));        System.out.println("jimmy 票数" + result.get("jimmy"));    }}