Binary Search in Java

Binary search is used to search a key element from multiple elements. Binary search is faster than linear search.

In case of binary search, array elements must be in ascending order. If you have unsorted array, you can sort the array using Arrays.sort(arr) method.

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);	
 }
}

Test it Now

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);
	}
}

Test it Now

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);
	}
}

Test it Now

Output: