上一篇介紹了負載均衡的輪詢，隨機，跟hash演算法，這邊我們一起了解下，加權的輪詢以及加權的隨機。其實理解好了輪詢跟隨機演算法，再加權的話其實是差不多的。

看面通過程式碼來了解：

（1）為了不重複建立一個server列表，我們先建立一個共有的server列表，如下：

	public static Map<String,Integer> ipMapList = new HashMap<String,Integer>();
	
	static{
		ipMapList.put("102.33.22.34", 3);
		ipMapList.put("102.33.21.35", 1); 
		ipMapList.put("102.33.23.36", 7); 
		ipMapList.put("102.33.24.37", 6); 
		ipMapList.put("102.33.25.38", 2);
		ipMapList.put("102.33.26.39", 2);
		ipMapList.put("102.33.27.11", 4);
		ipMapList.put("102.33.28.56", 8);
		ipMapList.put("102.33.29.56", 4);
		ipMapList.put("102.33.30.37", 9);
	}
 

private static volatile int pos = 0;
	
	public static String getServerIP(){
		String ip = null;
		Map<String,Integer> map = new HashMap<String,Integer>();
		map.putAll(IPMapList.ipMapList);
		Set<String> keySet = map.keySet();
		Iterator<String> iterator = keySet.iterator();
		List<String> list = new ArrayList<>();
		while(iterator.hasNext()){
			String server = iterator.next();
			int weight = map.get(server);
			for(int i=0;i<weight;i++){
				list.add(server);
			}
					
		}
 

		if(pos>list.size()) pos = 0;
		ip = list.get(pos);
		pos++;
		return ip;
	}
	public static void main(String[] args) {
		System.out.println(getServerIP());
	}

（3）加權隨機

	public static String getServerIp(){
		String ip = null;
		Map<String,Integer> map = new HashMap<String,Integer>();
		map.putAll(IPMapList.ipMapList);
		Set<String> keySet = map.keySet();
		Iterator<String> iterator = keySet.iterator();
		List<String> list = new ArrayList<>();
		
		while(iterator.hasNext()){
			String server = iterator.next();
			int weight = map.get(server);
			for(int i=0;i<weight;i++){
				list.add(server);
			}
		}
 

		Random random = new Random();
		int pos = random.nextInt(list.size());
		ip = list.get(pos);
		return ip;
	}
	public static void main(String[] args) {
		System.out.println(getServerIp());
	}