public class ConsistentHash<T> {

    //自定義hash方法
    private Hash<Object> hashMethod;

    //創(chuàng)建hash映射，虛擬節(jié)點(diǎn)映射真實(shí)節(jié)點(diǎn)
    private final Map<Integer, T> hashMap = new ConcurrentHashMap<>();

    //將所有的hash保存起來
    private List<Integer> keys = new ArrayList<>();

    //默認(rèn)虛擬節(jié)點(diǎn)數(shù)量
    private final int replicas;

    public ConsistentHash() {
        this(3, Utils::rehash);
    }

    public ConsistentHash(int replicas, Hash<Object> hashMethod) {
        this.replicas = replicas;
        this.hashMethod = hashMethod;
    }

    @SafeVarargs
    public final void add(T... keys) {
        for (T key : keys) {
            //根據(jù)虛擬節(jié)點(diǎn)個(gè)數(shù)來計(jì)算虛擬節(jié)點(diǎn)
            for (int i = 0; i < this.replicas; i++) {
                //根據(jù)函數(shù)獲取到對(duì)應(yīng)的hash值
                int hash = this.hashMethod.hash(i + ":" + key.toString());
                this.keys.add(hash);
                this.hashMap.put(hash, key);
            }
        }
        //排序，因?yàn)槭且粋€(gè)環(huán)狀結(jié)構(gòu)
        Collections.sort(this.keys);
    }

    /**
     * 根據(jù)對(duì)應(yīng)的key來獲取到節(jié)點(diǎn)信息
     *
     * @param key
     * @return
     */
    public T get(Object key) {
        Objects.requireNonNull(key, "key不能為空");
        int hash = this.hashMethod.hash(key);
        //獲取到對(duì)應(yīng)的節(jié)點(diǎn)信息
        int idx = Utils.search(this.keys.size(), h -> this.keys.get(h) >= hash);
        //如果idx == this.keys.size() ，就代表需要取 this.keys.get(0); 因?yàn)槭黔h(huán)狀，所以需要使用 % 來進(jìn)行處理
        return this.hashMap.get(this.keys.get(idx % this.keys.size()));
    }
}

@FunctionalInterface
public static interface Hash<T> {
    /**
     * 計(jì)算hash值
     *
     * @param t
     * @return int類型
     */
    int hash(T t);
}

public static class Utils {
		// int類型的最大數(shù)據(jù)
        static final int HASH_BITS = 0x7fffffff;

        /**
         * 通過二分查找法，定義數(shù)組索引位置
         *
         * @param len
         * @param f
         * @return
         */
        public static int search(int len, Function<Integer, Boolean> f) {
            int i = 0, j = len;
            //通過二分查找發(fā)來定為索引位置
            while (i < j) {
                //長度除于2
                int h = (i + j) >> 1;
                //調(diào)用函數(shù)，判斷當(dāng)前的索引值是否大于
                if (f.apply(h)) {
                    //向低半段進(jìn)行遍歷
                    j = h;
                } else {
                    //向高半段進(jìn)行遍歷
                    i = h + 1;
                }
            }
            return i;
        }

        /**
         * 將返回的hash能夠平均的計(jì)算在 int類型之間
         *
         * @param o
         * @return
         */
        public static int rehash(Object o) {
            int h = o.hashCode();
            return (h ^ (h >>> 16)) & HASH_BITS;
        }
    }

public static void main(String[] args) {
        ConsistentHash<String> consistentHash = new ConsistentHash<>();
        consistentHash.add("192.168.2.106", "192.168.2.107", "192.168.2.108");

        Map<String, Object> map = new HashMap<>();
        map.put("zs", "192.168.2.108");
        map.put("999999", "192.168.2.106");
        map.put("233333", "192.168.2.106");

        map.forEach((k, v) -> {
            String node = consistentHash.get(k);
            if (!v.equals(node)) {
                throw new IllegalArgumentException("節(jié)點(diǎn)獲取錯(cuò)誤，key：" + k + "，獲取到的節(jié)點(diǎn)值為：" + node);
            }
        });

        consistentHash.add("192.168.2.109");
        map.put("zs", "192.168.2.109");
        map.forEach((k, v) -> {
            String node = consistentHash.get(k);
            if (!v.equals(node)) {
                throw new IllegalArgumentException("節(jié)點(diǎn)獲取錯(cuò)誤，key：" + k + "，獲取到的節(jié)點(diǎn)值為：" + node);
            }
        });
    }