Binary Search

import java.util.*;

public class BinarySearch {
    
    public static final int NO_SUCH_KEY = -1;    
    
    public static int search(int[] keys, int key) {
        if(keys == null || keys.length == 0) 
            return NO_SUCH_KEY;

        return searchImpl(keys, key, 0, keys.length - 1);
    }

    private static int searchImpl(int[] keys, int key, int low, int high) {
        if(low > high) return NO_SUCH_KEY;
        
        int mid = (low + high) /2;
        if(key == keys[mid])
            return mid;
        else if(key < keys[mid])
            return searchImpl(keys, key, low, mid - 1);
        else 
            return searchImpl(keys, key, mid + 1, high);
    }

    public static void main(String[] args) {
        int[] keys = new int[10];
        Random rand = new Random();
        for(int i = 0; i < keys.length; i++) {
            keys[i] = rand.nextInt() % 1000;
        }
        Arrays.sort(keys);
        System.out.println(Arrays.toString(keys));

        Scanner sc = new Scanner(System.in);
        int k;
        while(true) {
            k = sc.nextInt();
            int i = search(keys, k);
            
            if(i == NO_SUCH_KEY) {
                System.out.println("Not found, would exit.");
                break;
            } else {
                System.out.println("Found, position:" + i);
            }
        }
    }
}