Make Selenium Easy

Frequently Asked Java Program 20: Java Program to Find Missing Alphabets in Given String

This program was asked in Siemens.

Problem Statement:

You need to find missing alphabets from a given string. E.g.

User input: “Amod Mahajan”

Output: [B, C, D, E, F, G, H, I, J, K, L, N, O, P, Q, R, S, T, U, V, W, X, Y, Z, b, c, e, f, g, i, k, l, p, q, r, s, t, u, v, w, x, y, z]


Logic step by step:

Step 1: Remove all whitespaces from given string as we just need characters of given string. To do this, we can use replaceAll() method of String class. I will remove all white spaces into empty space. E.g. userInput.replaceAll(” “, “”)

Step 2: We need to extract each character from given string and store in an array. We can do this using split() method. E.g.

String [] inputStringArray = userInput.split(“”);

Step 3: Create an array of alphabets including upper and lower alphabets.

String alphabets[]= “abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ”.split(“”);

Step 4: Now create a Set of above arrays. Set is useful to remove duplicate characters and find intersection of arrays.

Complete Java Program:

package StringPrograms;

import java.util.Arrays;
import java.util.HashSet;
import java.util.Scanner;

public class MissingAlphabets {

	public static void main(String[] args) {

		// User input for the string to know length
		Scanner sc = new Scanner(;
		System.out.println("Please enter the string to know the length:");

		String userInput = sc.nextLine();

		// We must close input stream

		System.out.println("You entered: " + userInput);
		// Replacing whitespace to empty as we are concerned about alphabets
		userInput= userInput.replaceAll(" ", "");
		System.out.println("User input without spaces :"+userInput);
		// Creating a String array containing each character of user input
		String [] inputStringArray = userInput.split("");
		// Creating a String array containing alphabets
		String alphabets[]= "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ".split("");
		// Creating HashSet to find intersections
		HashSet<String> s1 = new HashSet<String>(Arrays.asList(inputStringArray));
		HashSet<String> s2 = new HashSet<String>(Arrays.asList(alphabets));
		System.out.println("User Input in set :"+s1);
		System.out.println("Alphabets :"+s2);
		// Intersection of above sets
		// Missing alphabets
		System.out.println("Missing alphabets :"+ s2);


If you have any other optimal way of solving above problem, post in comment.


Author: Amod Mahajan

A software Tester who is paid to judge products developed by others. Currently getting paid in American Dollars. Writing technical posts and creating YouTube videos are my hobbies.

2 thoughts on “Frequently Asked Java Program 20: Java Program to Find Missing Alphabets in Given String

  1. Hi Amod,
    I have optimal way of doing this.

    String s=“Make Selenium Easy”;

    for(char c=‘a’; c<=‘z’; c++)
    { if(s.toLowerCase().indexOf(c)==-1) {

  2. import java.util.LinkedHashMap;
    import java.util.Scanner;

    public class MissingAlphabets {
    public static void main(String[] args) {

    String alphabets= “abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ”;

    Scanner sc = new Scanner(;
    System.out.println(“Please enter the string “);

    String userInput = sc.nextLine();

    System.out.println(“You entered: ” + userInput);
    userInput=userInput.replaceAll(” “, “”);
    LinkedHashMap map=new LinkedHashMap();
    for(int i=0;i<userInput.length();i++)



    System.out.println("Missing Alphabets – ");
    for(int i=0;i<alphabets.length();i++)
    if(map.get(alphabets.charAt(i)) == null)
    System.out.print(alphabets.charAt(i)+" ");
    // if you want to store in arraylist or some other collection class u can do that i am just printing


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