有序的key-value 取值和保存的实现

package find;

/**
 * @author: jian.tang
 * @description: 有序
 * @date: 2019/5/20 16:40
 */
public class BinarySearchST,Value> {

    private Key [] keys;
    private Value [] values;
    private int N;
    private BinarySearchST(int capacity)
    {
        keys = (Key[]) new Comparable[capacity];
        values = (Value[]) new Object[capacity];
    }
    public int size()
    { return  N ;}

    public boolean isEmpty(){
        return N == 0;
    }
    //针对有序的数组
    public Value get(Key key)
    {
        if (isEmpty()) return null;
        int i = rank(key);
        if (i < N && keys[i].compareTo(key) == 0)
            return values[i];
        else return null;
    }
    public void put(Key key,Value value)
    {
        int mid = rank(key);
        if (mid < N && keys[mid].compareTo(key) == 0){
            values[mid] = value;
            return;
        }
        for (int j = N; j > mid; j --)
        {
            keys[j] = keys[j -1];
            values[j] = values[j - 1];
        }
        keys[mid] = key;
        values[mid] = value;
        N++;
    }
    //判断该值是否比中间的大返回该值对应的索引  递归该方法返回 该key最终对应的索引
    public int rank(Key key)
    {
        int lo = 0, hi = N -1;
        while (lo <= hi)
        {
            int mid = lo + hi - lo / 2;
            int cmp = key.compareTo(keys[mid]);
            if (cmp > 0) return hi = mid + 1;
            else if (cmp < 0) return hi = mid - 1;
            else return  mid;
        }
        return  lo;
    }
}