Find number in array

Problem :  Write a method that takes a sorted array A of integers and a key k

return the index of first occurrence  of k h A return -l if k does Rot

appear in A. Write tests to verify your code.

what is best case scenario is your key index 0 and worst case is last element which takes o(n) within large  array even sorted it takes time to find index in array size 2^10

Let's figure out using binary search 

package Search;
/**
 * Write a method that takes a sorted array A of integers and a key k md
retums the hdex of first occurrmce of k h A Retum -l if k does Rot
appear in A. Write tests to verify your code.
 * @author Mohamed fawzy
 * @copyright GPL
 */
public class BinarySearch {
 
 public static int search(int a[], int k){
  int low=0;
  int high= a.length-1;
  int middle;
  while(low <= high){
   middle = low + (high - low) /2;
   if(a[middle]==k){
    return middle;
   }else if(a[middle] < k){
    low = middle+1;
   }else{
    high = middle-1;
   }
  }
  return -1;
 }
}

Test case :

package Search;

public class BinarySearchTest {
 
 public static void main(String[] args){
  int[] array = {1,2,3,4,6,10,15,20};
  int k = 10;
  BinarySearch binarysearch = new BinarySearch();
  int index = binarysearch.search(array, k);
  System.out.println(index);
 }

}