架构师训练营第 5 周命题作业

package algorithm.hash;
import java.util.Collection;import java.util.SortedMap;import java.util.TreeMap;
public class ConsistentHash<T> {
    // 虚拟节点的数量    private final int virtualNodeNum;
    private final SortedMap<Integer, T> consistenHashCircle = new TreeMap<Integer, T>();
    public ConsistentHash(int virtualNodeNum, Collection<T> nodes) {        this.virtualNodeNum = virtualNodeNum;        for (T node : nodes) {            add(node);        }    }
    // 新增一个实际节点    public void add(T node) {        for (int i = 0; i < virtualNodeNum; i++) {            String nodestr = node.toString() + Math.pow((double) i, (double) 6);            int hashcode = nodestr.hashCode();            consistenHashCircle.put(hashcode, node);
        }    }
    // 删除一个实际节点    public void remove(T node) {        for (int i = 0; i < virtualNodeNum; i++) {            String nodestr = node.toString() + Math.pow((double) i, (double) 6);            consistenHashCircle.remove(nodestr.hashCode());        }    }
    // 获取数据要存放的实际节点    public T get(Object key) {        if (consistenHashCircle.isEmpty()) {            return null;        }        int hash = key.hashCode();        if (!consistenHashCircle.containsKey(hash)) {            SortedMap<Integer, T> tailMap = consistenHashCircle.tailMap(hash);            hash = tailMap.isEmpty() ? consistenHashCircle.firstKey() : tailMap.firstKey();        }        return consistenHashCircle.get(hash);    }
}

package algorithm.hash;
import java.util.HashSet;import java.util.Random;import java.util.Set;
public class ConsistentHashTest<T> {
    // 求和    static int Sum(int[] data) {        int sum = 0;        for (int i = 0; i < data.length; i++)            sum = sum + data[i];        return sum;    }
    // 求平均值    static double Mean(int[] data) {        int mean = 0;        mean = Sum(data) / data.length;        return mean;    }
    // 求总体方差    static double POP_Variance(int[] data) {        double variance = 0;        for (int i = 0; i < data.length; i++) {            variance = variance + (Math.pow((data[i] - Mean(data)), 2));        }        variance = variance / data.length;        return variance;    }
    // 求总体标准差    static double POP_STD_dev(int[] data) {        double std_dev;        std_dev = Math.sqrt(POP_Variance(data));        return std_dev;    }
    // 求样本方差    static double Sample_Variance(int[] data) {        double variance = 0;        for (int i = 0; i < data.length; i++) {            variance = variance + (Math.pow((data[i] - Mean(data)), 2));        }        variance = variance / (data.length - 1);        return variance;    }
    // 求样本标准差    static double Sample_STD_dev(int[] data) {        double std_dev;        std_dev = Math.sqrt(Sample_Variance(data));        return std_dev;    }
    public static void main(String[] args) {        Set<String> nodes = new HashSet<String>();        int[] countArrays = new int[10];        for (int i = 1; i < 11; i++) {            nodes.add("192.168.0." + i);            countArrays[i - 1] = 0;
        }
        ConsistentHash<String> consistentHash = new ConsistentHash<String>(200, nodes);
        Random random = new Random();        for (int i = 0; i < 1000000; i++) {            String node = consistentHash.get("" + random.nextInt(1000000) + System.currentTimeMillis() % 100);            switch (node) {                case "192.168.0.1":                    countArrays[0]++;                    break;                case "192.168.0.2":                    countArrays[1]++;                    break;                case "192.168.0.3":                    countArrays[2]++;                    break;                case "192.168.0.4":                    countArrays[3]++;                    break;                case "192.168.0.5":                    countArrays[4]++;                    break;                case "192.168.0.6":                    countArrays[5]++;                    break;                case "192.168.0.7":                    countArrays[6]++;                    break;                case "192.168.0.8":                    countArrays[7]++;                    break;                case "192.168.0.9":                    countArrays[8]++;                    break;                case "192.168.0.10":                    countArrays[9]++;                    break;            }        }
        System.out.println("总体标准差为：" + POP_STD_dev(countArrays));        System.out.println("样本标准差为：" + Sample_STD_dev(countArrays));    }
}

总体标准差为：5798.654309406623样本标准差为：6112.318327225222
总体标准差为：5972.901120895942样本标准差为：6295.99059366797
总体标准差为：5788.0663956108865样本标准差为：6101.157686137207
总体标准差为：5662.06605401244样本标准差为：5968.341664333756
体标准差为：5969.317867227377样本标准差为：6292.21351265903