"Discover frequently asked Java programming interview questions and logical programs, such as reversing a number. Explore essential Java features, the Singleton design pattern, and the Java Virtual Machine (JVM).

Top 20 Java Programming Interview Questions and Logical Programs

Santosh Kumar Gadagamma October 8, 2023 Interview Stuff, Java Language Comments Off on Top 20 Java Programming Interview Questions and Logical Programs 365 Views

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Java programming interview questions

Java programming interview questions often test your knowledge of core programming concepts. One common task is reversing a number, which can be accomplished using different approaches. Let’s dive into some frequently asked Java interview questions and explore program examples for reversing numbers.

Java programming interview questions include about key language features, such as immutability in strings and the usage of StringBuffer and StringBuilder. It’s essential to understand the differences between these concepts to excel in Java interviews.
One of the essential design patterns in Java is the Singleton pattern, which ensures that a class has only one instance. Understanding how to implement this pattern can showcase your proficiency in Java development.
The Java Virtual Machine (JVM) is the heart of Java’s platform independence. Being familiar with its role and how it executes Java bytecode can help you tackle questions about Java’s cross-platform compatibility.
Logical programming challenges, like reversing a number, are also common in Java interviews. The provided code examples demonstrate different approaches to solving such problems, offering valuable insights into Java’s syntax and control structures.

1. Reversing Numbers with a While Loop: You can reverse a number using a while loop by repeatedly extracting the last digit and appending it to the reverse. This method is efficient and straightforward.

2. Reversing Numbers with a For Loop: A for loop can also be used to reverse a number by iterating through its digits and constructing the reverse number in the process. It offers a concise way to achieve the desired result.

3. Reversing Numbers with Recursion: Recursion is a powerful technique to reverse numbers in Java. By breaking down the problem into smaller parts and leveraging the recursive call stack, you can efficiently reverse numbers of any length.

These Java programming interview questions not only test your coding skills but also your problem-solving ability. Whether you’re a beginner or an experienced Java developer, mastering these techniques is essential for acing Java interviews and building robust Java programs.

Java programming interview questions – Logical Programs Useful at Interview

1. Write program to print the reverse of a number?

Finding of the reverse can be done in different ways, see the below.

Reverse of a number by using While loop:

import java.util.Scanner;

public class ReverseofNumberByWhile {
public int ReverseByWhile() {

int number = 0;
int reverse = 0;
System.out.println(“Enter a number to find its reverse: “);
Scanner in = new Scanner(System.in);
// To get the runtime input
number = in.nextInt();
while (number != 0) {
reverse = reverse * 10;
reverse = reverse + number % 10;
number = number / 10;
}

System.out.println(“Reverse of input “+number+” is “+reverse);
return reverse;
}

/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
ReverseofNumberByWhile rev = new ReverseofNumberByWhile();
rev.ReverseByWhile();
}
}

Output is :

Enter a number to find its reverse:
123456
Reverse of input 123456 is 654321

Reverse of Number By using For Loop:

import java.util.Scanner;

public class ReverseofNumber {
int number;
int reverse = 0;
Scanner sr = new Scanner(System.in);

public int reverseByforloop() {
System.out.println(“Enter an intger value”);
number = sr.nextInt();

for (; number != 0; number /= 10) { // Initialization not required
int reminder = number % 10;
reverse = reverse * 10 + reminder;
}
System.out.println(“Reverse of by using for loop ” + number + ” “+ reverse);
return reverse;
}

/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
ReverseofNumber rn = new ReverseofNumber();
rn.reverseByforloop();
}

}

Output:

Enter an integer value : 5678
Reverse of by using for loop : 8765

Reverse of Number By using For Recursion:

import java.util.Scanner;

public class ReverseByRecursion {
public static void reverseOfNumber(int input_number) {
if (input_number < 10) {
System.out.println(input_number);
return;
}
else {
System.out.print(input_number % 10);
//Method is calling itself: recursion
reverseOfNumber(input_number/10);
}
}

/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
int number=0;
System.out.println(“Enter a number to find its reverse: “);
Scanner sr = new Scanner(System.in);
number = sr.nextInt();
System.out.print(“Reverse of input”+ number+” is:”);
reverseOfNumber(number);
System.out.println();

}

}

Output is:

Enter a number to find its reverse: 4567
Reverse of input4567 is:7654

Official documentation on Java Programming from Oracle.

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Top 20 Java Programming Interview Questions and Logical Programs

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