Solution :- 

class BinarySearch
{
public static void bs(int arr[],int first , int last,int key)
{
int mid = (first + last)/2;
while (first<=last)
{
if(arr[mid]<key)
{
first=mid +1;
}
else if(arr[mid]==key)
{
System.out.println(“Element is found at index :- “+mid);
break;
}
else
{
last = mid -1;
}
mid = (first + last)/2;
}
if(first > last)
{
System.out.println(“Element is not Found”);
}
}
public static void main(String args[])
{
int arr[]={10,20,30,40,50};
int key = 30;
int last=arr.length-1;
bs(arr,0,last,key);
}
}

Output :-