Java Programming Interview Questions with Answers (Part-1)

Hello Friends, I hope you guys are safe and doing great work. Today I am going to discuss some Java interview questions. I am trying to give as simple codes as possible. I have been preparing this MEGA list for quite some time and now It's ready to share with you guys.

I have also worked hard to keep this list up-to-date to include what interviewers are asking nowadays and what will be asked in the upcoming years

Question 1 - Calculate the Factorial of a number with and without Recursion in Java.

Before starting coding, I explain how we dry run the program. It will easily help you to understand the flow of the program.

Let's take an example 5. num = 5; fact = 1; //5*4*3*2*1

fact 1 = fact; // 1 *1 =1

fact *2= fact; // 1**2=2

fact * 3 = fact; *// 2**3=6

fact * 4= fact; *// 6**4=24

fact * 5 = fact; *// 24**5=120

Now, let's start Coding. The class name of my program is factorialclass.

public class factorialclass(){
    public static void main(String[] args){
       int num = 5;
       fact = 1;
       for(int i=1; i<=num; i++){
          fact = fact * i;
       }
        System.out.println ("Factorial of " + num + " is - " + fact);
    }
}

Using function:-

public class factorialclass(){
    public static void main(String[] args){
       int num = 5;
       int ans = 1;
       answer = fact(num);
        System.out.println ("Factorial of " + num + " is - " + ans);
    }
      static int fact(int a){
      int b = 1;
      for(int i=1; i<=a; i++){
          b = b* i;
       }
       return b;
      } 
}

Next, we write this code using the Recursive Function. Recursive means a function that calls itself to break down a problem into smaller, subproblems.

public class factorialclass(){
    public static void main(String[] args){
       int num = 5;
       int ans = 1;
       answer = fact(num);
        System.out.println ("Factorial of " + num + " is - " + ans);
    }
      static int fact(int a){
         if(a<=1){
           return 1;
          }else{
           return a*fact(a-1);
          }
      }
}

Question 2 - Write a program to find the sum of Digits of a given number.

I am giving here a small overview of my program.

package com.mycompany.java_practice_questions;

import java.util.Scanner;

public class Sum_of_digits {
    public static void main(String[] args) {
        int num = 0, sum = 0, rem = 0; 
        Scanner scan = new Scanner(System.in);
        System.out.println("Please enter a number");
        num = scan.nextInt();

        while(num > 0){
            rem = num %10;
            sum = sum + rem;
            num = num /10;

        }
        System.out.println(sum);
    }
}