hash 一致性算法

package learn;
import java.util.List;import java.util.SortedMap;import java.util.TreeMap;
public class ConsistentHashing {    private SortedMap<Integer, String> virtualNodes = new TreeMap<>();
    public ConsistentHashing(String[] serverList, int virtualNodeCount){        for(String server: serverList) {            for(int i = 0; i< virtualNodeCount; i++){                String virtualName = server + "@" + i;                int hash = getHash(virtualName);                this.virtualNodes.put(hash, virtualName);            }        }    }    public String getServer(String key){        String virtualNode;        int hash = getHash(key);        SortedMap<Integer, String> subMap = this.virtualNodes.tailMap(hash);        if(subMap.isEmpty()){            int nodeKey = this.virtualNodes.firstKey();            virtualNode = this.virtualNodes.get(nodeKey);        }else{            virtualNode = this.virtualNodes.get(subMap.firstKey());        }        return virtualNode.substring(0, virtualNode.indexOf("@"));    }
    private static int getHash(String str){        final int p = 16777619;        int hash = (int)2166136261L;        for (int i = 0; i < str.length(); i++)            hash = (hash ^ str.charAt(i)) * p;        hash += hash << 13;        hash ^= hash >> 7;        hash += hash << 3;        hash ^= hash >> 17;        hash += hash << 5;        // 如果算出来的值为负数则取其绝对值        if (hash < 0)            hash = Math.abs(hash);        return hash;    }}

import learn.ConsistentHashing;
import java.util.*;
public class HelloWorld {    static ArrayList<String> arrayList;    public static void main(String[] args){        String[] serverList = {"192.168.3.30","192.168.3.31", "192.168.3.32", "192.168.3.33","192.168.3.34",                "192.168.3.35",  "192.168.3.36", "192.168.3.37", "192.168.3.38", "192.168.3.39"};        Map<String, Integer> countMap = new HashMap<>();        ConsistentHashing consistentHashing = new ConsistentHashing(serverList, 150);        for(int i=0; i<1000000; i++){             String server = consistentHashing.getServer("test" + i);             if (countMap.containsKey(server)){                 Integer count = countMap.get(server);                 countMap.put(server, count+1);            }else{                 countMap.put(server, 1);             }        }        double value = getStandardDeviation(countMap, 100000, 10);        System.out.println(countMap.toString());        System.out.println("标准差为：" + value);    }
    public static double getStandardDeviation(Map<String,Integer> countMap, int avg, int count){        int total = 0;        for(Map.Entry<String,Integer> entry : countMap.entrySet()){            total += (entry.getValue() - avg) *(entry.getValue() - avg);        }        return Math.sqrt(total/count);    }}