第五周作业一

class ConsistentHashing {
 private HashFunction hashFunction;
 private int replicas;
 private TreeMap<Integer> circle = new TreeMap<Integer>();
 public ConsistentHash(HashFunction hashFunction, int replicas, Collection<T> nodes) {
   this.hashFunction = hashFunction;
   this.replicas = replicas;
   for (T node : nodes) {
     add(node);
   }
 }
 public void add(T node) {
   for (int i = 0; i < replicas; i++) {
     circle.put(hashFunction.hash(node.toString() + i), node);
   }
 }
 public void remove(T node) {
   for (int i = 0; i < replicas; i++) {
     circle.remove(hashFunction.hash(node.toString() + i));
   }
 }
 public T get(Object key) {
   if (circle.isEmpty()) {
     return null;
   }
   int hash = hashFunction.hash(key);
   if (!circle.containsKey(hash)) {
     TreeMap<Integer> tailMap = circle.tailMap(hash);
     hash = tailMap.isEmpty() ? circle.firstKey() : tailMap.firstKey();
   }
   return circle.get(hash);
 }
}