二分（折半）查找

public class BinarySearch {

    public static void main(String[] args) {
        int[] array={1,2,3,4,5,6,7,8,9,10,11};
        System.out.println(binarySearch(array,11));
    }
    private static int binarySearch(int[] array,int key){
        int high=array.length-1;
        int low=0,mid=0;
        while(low<=high){
            mid=(high+low)/2;
            if(key==array[mid]){
                return mid;
            }else if(key<array[mid]){
                high=mid-1;
            }else{
                low=mid+1;
            }
        }
        return -1;
    }

}