Java Program to Implement Binary Search Algorithm

Example: Java Program to Implement Binary Search Algorithm

import java.util.Scanner;

// Binary Search in Java

class Main {
  int binarySearch(int array[], int element, int low, int high) {

    // Repeat until the pointers low and high meet each other
    while (low <= high) {

      // get index of mid element
      int mid = low + (high - low) / 2;

      // if element to be searched is the mid element
      if (array[mid] == element)
        return mid;

      // if element is less than mid element
      // search only the left side of mid
      if (array[mid] < element)
        low = mid + 1;

      // if element is greater than mid element
      // search only the right side of mid
      else
        high = mid - 1;
    }

    return -1;
  }

  public static void main(String args[]) {

    // create an object of Main class
    Main obj = new Main();

    // create a sorted array
    int[] array = { 3, 4, 5, 6, 7, 8, 9 };
    int n = array.length;

    // get input from user for element to be searched
    Scanner input = new Scanner(System.in);

    System.out.println("Enter element to be searched:");

    // element to be searched
    int element = input.nextInt();
    input.close();

    // call the binary search method
    // pass arguments: array, element, index of first and last element
    int result = obj.binarySearch(array, element, 0, n - 1);
    if (result == -1)
      System.out.println("Not found");
    else
      System.out.println("Element found at index " + result);
  }
}

Output 1

Enter element to be searched:
6
Element found at index 3

Here, we have used the Java Scanner Class to take input from the user. Based on the input from user, we used the binary search to check if the element is present in the array.

We can also use the recursive call to perform the same task.

  int binarySearch(int array[], int element, int low, int high) {

    if (high >= low) {
      int mid = low + (high - low) / 2;

      // check if mid element is searched element
      if (array[mid] == element)
        return mid;

      // Search the left half of mid
      if (array[mid] > element)
        return binarySearch(array, element, low, mid - 1);

      // Search the right half of mid
      return binarySearch(array, element, mid + 1, high);
    }

    return -1;
  }

Here, the method binarySearch() is calling itself until the element is found or, the if condition fails.

If you want to learn more about the binary search algorithm, visit Binary Search Algorithm.