Overview of Binary Search

Basic Overview:

  • A binary search algorithm finds the position of a specified input value within an array sorted by key value.

  • For binary search, the array should be sorted i.e. arranged in ascending or descending order.

  • In Binary search, the search key value with the key value of the middle element of the array. If the key element match, then a matching element has been found and its position, is returned.

  • If the search key is less than the middle element's key, then the algorithm repeats its action on the sub-array to the left of the middle element or, if the search key is greater, on the sub-array to the right.

  • If the remaining array to be searched is empty, then the key cannot be found in the array and a “key is not found” message returned.

Steps are as follows:

  • Create new java class

  • create a new java class

  • Write the code for binary search algorithm as follows:

  • package com.javabykiran.binarysearch;
    import java.util.Scanner;
    public class JbkBinarySearch {
        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[];
    	int counter = 0;
    	Scanner input = new Scanner(System.in);
    	System.out.println("Enter total number of elements :");
    	int numberOfElements = input.nextInt();
    	// Creating array to store the numbers of size n
    	arr = new int[numberOfElements];
    	System.out.println("Enter " + numberOfElements + " integers in ascending order");
    	// Loop to store each entered number in array
    	for (counter = 0; counter < numberOfElements; counter++)
                arr[counter] = input.nextInt();
            System.out.println("Enter a key to be seached");
    	int key = input.nextInt();
    	int last = arr.length - 1;
    	int result = binarySearch(arr, 0, last, key);
    	if (result == -1)
                System.out.println("Element is not found!");
                System.out.println("Element is found at index: " + result);
  • Now run the programs as Java Application

  • Enter the total number of elements on console.

  • Enter the elements one by one in ascending order.

  • Enter the number to be searched and the key will be searched.

  • Press Enter to check whether element is present or not in array.

  • Output Window:

  • binary search program output