架构师训练营 - 第五周作业

public class Node {
    private Node(){}
    public Node(String name,String ip){
        this.name=name;
        this.ip=ip;
    }
    private String name;
    private String ip;
    public long getCount() {
        return count.get();
    }
    public AtomicLong count=new AtomicLong(0);
    public void incr(){
        count.incrementAndGet();
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getIp() {
        return ip;
    }
    public void setIp(String ip) {
        this.ip = ip;
    }
}

public class NodePool {
    // 实例节点列表
    private  List<Node> nodeList=null;
    // 虚拟节点列表
    private TreeMap<Integer,Node> hashMaps=new TreeMap<>();
    // 实例节点转为多少个虚拟节点
    private int virtualNum;
    private NodePool(){}
    public NodePool(List<Node> nodeList,int virtualNum){
        this.nodeList=nodeList;
        this.virtualNum=virtualNum;
        for(Node node:nodeList){
            for (int i = 0; i <virtualNum ; i++) {
                int hash=hashCode(node.getName()+"-"+i);
                hashMaps.put(hash,node);
            }
        }
    }
    public Node getNodeObj(int key){
        Map.Entry<Integer, Node> nodeEntry = getHashMaps().ceilingEntry(key);
        if(nodeEntry==null)nodeEntry=getHashMaps().firstEntry();
        return nodeEntry.getValue();
    }
    public static int hashCode(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);
//        }
        //System.out.println(hash);
        return hash;
    }
    public List<Node> getNodeList() {
        return nodeList;
    }
    public TreeMap<Integer, Node> getHashMaps() {
        return hashMaps;
    }
    public int getVirtualNum() {
        return virtualNum;
    }
}

public class HashDemo {
    public static void main(String[] args) {
        List<Node> nodeList=new ArrayList<>();
        nodeList.add(new Node("node01","192.168.0.11"));
        nodeList.add(new Node("node02","192.168.0.12"));
        nodeList.add(new Node("node03","192.168.0.13"));
        nodeList.add(new Node("node04","192.168.0.14"));
        nodeList.add(new Node("node05","192.168.0.15"));
        nodeList.add(new Node("node06","192.168.0.16"));
        nodeList.add(new Node("node07","192.168.0.17"));
        nodeList.add(new Node("node08","192.168.0.18"));
        nodeList.add(new Node("node09","192.168.0.19"));
        nodeList.add(new Node("node10","192.168.0.20"));
        NodePool nodePool1 = new NodePool(nodeList,50);
        NodePool nodePool2 = new NodePool(nodeList,100);
        NodePool nodePool3 = new NodePool(nodeList,150);
        NodePool nodePool4 = new NodePool(nodeList,200);
        NodePool nodePool5 = new NodePool(nodeList,250);
        HashDemo hashDemo = new HashDemo();
        hashDemo.display(nodePool1);
        hashDemo.display(nodePool2);
        hashDemo.display(nodePool3);
        hashDemo.display(nodePool4);
        hashDemo.display(nodePool5);
    }
    public void display(NodePool nodePool){
        Integer nKey;
        for (int i = 0; i <1000000 ; i++) {
            nKey=NodePool.hashCode("key"+i);
            Node nodeObj = nodePool.getNodeObj(nKey);
            nodeObj.incr();
        }
        /*
            计算平方差
         */
        List<Double> tmpList1=new ArrayList();
        for(Node node:nodePool.getNodeList()){
//            System.out.println("nodeName="+node.getName()+",count="+node.getCount());
            tmpList1.add(Double.parseDouble(node.getCount()+""));
        }
        System.out.println(nodePool.getVirtualNum()+"个虚拟节点，平方差为:"+getStandardDiviation(tmpList1));
    }
    public double getStandardDiviation(List<Double> x) {
        int m = x.size();
        double sum = 0;
        for (int i = 0; i < m; i++) {// 求和
            sum += x.get(i);
        }
        double dAve = sum / m;// 求平均值
        double dVar = 0;
        for (int i = 0; i < m; i++) {// 求方差
            dVar += (x.get(i) - dAve) * (x.get(i) - dAve);
        }
        return Math.sqrt(dVar / m);
    }
}

50个虚拟节点，平方差为:13551.925449913013
100个虚拟节点，平方差为:18109.49825920089
150个虚拟节点，平方差为:20364.833738579848
200个虚拟节点，平方差为:24623.291112278228
250个虚拟节点，平方差为:27584.167400884155