二分查找Java实现

public class BinarySearch {
    public static int rank(int key, int[] a){
        int lo = 0;
        int hi = a.length - 1;
        while( lo <= hi){
            int mid = lo + (hi - lo) / 2;
            if (key < a[mid]) {
                hi = mid - 1;
            }else if(key > a[mid]){
                lo = mid + 1;
            }else{
                return mid;
            }
        }
        return -1;
    }
}

	
	public static int recursionBinarySearch(int[] arr,int key,int low,int high){
		
		if(key < arr[low] || key > arr[high] || low > high){
			return -1;				
		}
		
		int middle = (low + high) / 2;			//初始中间位置
		if(arr[middle] > key){
			//比关键字大则关键字在左区域
			return recursionBinarySearch(arr, key, low, middle - 1);
		}else if(arr[middle] < key){
			//比关键字小则关键字在右区域
			return recursionBinarySearch(arr, key, middle + 1, high);
		}else {
			return middle;
		}	
		
	}