Binary Search in Java

Binary Search Example in Java

Let's see an example of binary search in java.

class BinarySearchExample{  
 public static void binarySearch(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;  
        binarySearch(arr,0,last,key);     
 }  
}  

Output:

Element is found at index: 2

Binary Search Example in Java using Recursion

Let's see an example of binary search in java where we are going to search an element from an array using recursion.

class BinarySearchExample1{  
    public static int binarySearch(int arr[], int first, int last, int key){  
        if (last>=first){  
            int mid = first + (last - first)/2;  
            if (arr[mid] == key){  
            return mid;  
            }  
            if (arr[mid] > key){  
            return binarySearch(arr, first, mid-1, key);//search in left subarray  
            }else{  
            return binarySearch(arr, mid+1, last, key);//search in right subarray  
            }  
        }  
        return -1;  
    }  
    public static void main(String args[]){  
        int arr[] = {10,20,30,40,50};  
        int key = 30;  
        int last=arr.length-1;  
        int result = binarySearch(arr,0,last,key);  
        if (result == -1)  
            System.out.println("Element is not found!");  
        else  
            System.out.println("Element is found at index: "+result);  
    }  
}  

Output:

Element is found at index: 2

Binary Search Example in Java using Arrays.binarySearch()

import java.util.Arrays;  
class BinarySearchExample2{  
    public static void main(String args[]){  
        int arr[] = {10,20,30,40,50};  
        int key = 30;  
        int result = Arrays.binarySearch(arr,key);  
        if (result < 0)  
            System.out.println("Element is not found!");  
        else  
            System.out.println("Element is found at index: "+result);  
    }  
}  

Output:

Element is found at index: 2