Java负载均衡-輪詢法

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;

/**
 * <p>标    题: Java应用代码块</p>
 * <p>描    述: 負載均衡算法，輪詢法</p>
 * <p>版    权: Copyright (c) 2017  </p>
 * <p>公    司: 上海泓智信息科技有限公司</p>
 * <p>创建时间: 2017-6-28 下午03:48:01</p>
 * <p>@author zhengwei</p>
 * <p>@version 1.0</p>
 * <p>TestRoundRobin.java</p>
 */
public class TestRoundRobin {

    //存放服务器IP
    static Map<String,Integer> serverWeigthMap  = new HashMap<String,Integer>();

    //可通过数据库或配置文件加载
    static{
        serverWeigthMap.put("192.168.1.12", 1);
        serverWeigthMap.put("192.168.1.13", 1);
        serverWeigthMap.put("192.168.1.14", 2);
        serverWeigthMap.put("192.168.1.15", 2);
        serverWeigthMap.put("192.168.1.16", 3);
        serverWeigthMap.put("192.168.1.17", 3);
        serverWeigthMap.put("192.168.1.18", 1);
        serverWeigthMap.put("192.168.1.19", 2);
    }
     Integer  pos = 0;
     public  String roundRobin(){

        //重新建立一個map,避免出現由於服務器上線和下線導致的並發問題
        Map<String,Integer> serverMap  = new HashMap<String,Integer>();
        serverMap.putAll(serverWeigthMap);
        //獲取ip列表list
        Set<String> keySet = serverMap.keySet();
        ArrayList<String> keyList = new ArrayList<String>();
        keyList.addAll(keySet);

        String server = null;

        synchronized (pos) {
            if(pos >=keySet.size()){
                pos = 0;
            }
            server = keyList.get(pos);
            pos ++;
        }
        return server;
    }

    public static void main(String[] args) {
        TestRoundRobin robin = new TestRoundRobin();
        for (int i = 0; i < 20; i++) {
            String serverIp = robin.roundRobin();
            System.out.println(serverIp);
        }

    }

}