Top 10 Java Interview Question

Top 5 Java Programming Interview Questions for Beginners

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Top 5 Java Programming Interviews Preparing for a Java programming interview can be a challenging task, as employers often assess candidates’ technical skills and problem-solving abilities. In this blog post, we will highlight the top five essential Java programming concepts that every candidate should master to excel in interviews. By understanding and practicing these concepts, you can increase your chances of success and confidently tackle Java-related questions during the interview process.
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Java-Programming-Interview-Questions Top 5 Java Programming Interview Questions for Beginners

(1) Write a Java program to check the prime number

public class PrimeNumberChecker {
    public static boolean isPrime(int number) {
        if (number <= 1) {
            return false;
        }

        // Check for divisibility from 2 to the square root of the number
        for (int i = 2; i <= Math.sqrt(number); i++) {
            if (number % i == 0) {
                return false;
            }
        }

        return true;
    }

    public static void main(String[] args) {
        int number = 29;

        if (isPrime(number)) {
            System.out.println(number + " is a prime number.");
        } else {
            System.out.println(number + " is not a prime number.");
        }
    }
}

In this program, the isPrime() method takes an integer as input and checks if it is prime or not. It returns true if the number is prime and false otherwise.

The program demonstrates the usage of the isPrime() method by checking if the number 29 is prime or not. You can modify the number variable to check for different numbers.

The program uses a simple approach to check for divisibility from 2 to the square root of the number. If the number is divisible by any of these values, it is not prime. Otherwise, it is prime.

When you run the program, it will output whether the given number is prime. In this case, it will output “29 is a prime number.”
Top 5 Java Programming Interview

[embedyt] https://www.youtube.com/embed?listType=playlist&list=PL92c0di50EKBbgn_Gn6-hjP122miVOMm1[/embedyt]

(2) Java Program to Print Even and Odd Numbers?

public class EvenOddNumbers {
    public static void printEvenOddNumbers(int start, int end) {
        System.out.println("Even numbers:");
        for (int i = start; i <= end; i++) {
            if (i % 2 == 0) {
                System.out.print(i + " ");
            }
        }

        System.out.println("\nOdd numbers:");
        for (int i = start; i <= end; i++) {
            if (i % 2 != 0) {
                System.out.print(i + " ");
            }
        }
    }

    public static void main(String[] args) {
        int start = 1;
        int end = 20;

        printEvenOddNumbers(start, end);
    }
}

In this program, the printEvenOddNumbers() method takes the starting and ending numbers as input and prints the even and odd numbers within that range. The program demonstrates the usage of the printEvenOddNumbers() method by providing the starting number as 1 and the ending number as 20. You can modify the start and end variables to print even and odd numbers within a different range. The program uses a for loop to iterate through the numbers from the starting to the ending number. It checks whether each number is even or odd using the modulo operator %. If the remainder is 0 for the even numbers, it prints them. If the remainder is not 0 for the odd numbers, it prints them. When you run the program, it will output the even numbers followed by the odd numbers within the specified range. For example:

Even numbers:
2 4 6 8 10 12 14 16 18 20 
Odd numbers:
1 3 5 7 9 11 13 15 17 19

(3) Java Program for Armstrong Number

public class ArmstrongNumber {
    public static boolean isArmstrongNumber(int number) {
        int originalNumber = number;
        int sum = 0;

        // Calculate the sum of the cubes of each digit
        while (number != 0) {
            int digit = number % 10;
            sum += Math.pow(digit, 3);
            number /= 10;
        }

        // Check if the sum is equal to the original number
        return sum == originalNumber;
    }

    public static void main(String[] args) {
        int number = 153;

        if (isArmstrongNumber(number)) {
            System.out.println(number + " is an Armstrong number.");
        } else {
            System.out.println(number + " is not an Armstrong number.");
        }
    }
}

In this program, the isArmstrongNumber() method takes an integer as input and checks if it is an Armstrong number or not. It returns true if the number is an Armstrong number and false otherwise. The program demonstrates the usage of the isArmstrongNumber() method by checking if the number 153 is an Armstrong number or not. You can modify the number variable to check for different numbers. The program calculates the sum of the cubes of each digit in the number. It uses a while loop to extract each digit from the number and adds the cube of the digit to the sum. Finally, it compares the sum with the original number to determine if it is an Armstrong number. When you run the program, it will output whether the given number is an Armstrong number or not. In this case, it will output “153 is an Armstrong number.Top 5 Java Programming Interview

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4 . Write a Java Program to Swap Two Numbers Without a Third Variable

public class NumberSwapper {
    public static void swapNumbers(int a, int b) {
        System.out.println("Before swapping: a = " + a + ", b = " + b);

        a = a + b;
        b = a - b;
        a = a - b;

        System.out.println("After swapping: a = " + a + ", b = " + b);
    }

    public static void main(String[] args) {
        int num1 = 10;
        int num2 = 20;

        swapNumbers(num1, num2);
    }
}

In this program, the swapNumbers() method takes two integers as input, a and b, and swaps their values without using a third variable. The program demonstrates the usage of the swapNumbers() method by providing two numbers, num1, and num2, as 10 and 20, respectively. You can modify the values of num1 and num2 to swap different numbers. The program performs the swapping using arithmetic operations. It first adds the values of a and b and assigns the result to a. Then, how it subtracts the original value of b from a and assigns the result to b. Finally, it subtracts the original value of b from a to obtain the original value of a. Top 5 Java Programming Interview

Before swapping: a = 10, b = 20
After swapping: a = 20, b = 10

5. Find Minimum and Maximum Numbers in Java Array

public class MinMaxFinder {
    public static void findMinMax(int[] array) {
        if (array == null || array.length == 0) {
            System.out.println("Array is empty.");
            return;
        }

        int min = array[0];
        int max = array[0];

        for (int i = 1; i < array.length; i++) {
            if (array[i] < min) {
                min = array[i];
            }

            if (array[i] > max) {
                max = array[i];
            }
        }

        System.out.println("Minimum number: " + min);
        System.out.println("Maximum number: " + max);
    }

    public static void main(String[] args) {
        int[] numbers = { 4, 2, 9, 7, 1, 5 };

        findMinMax(numbers);
    }
}

In this program, the findMinMax() method takes an array of integers as input and finds the minimum and maximum numbers in the array. The program demonstrates the usage of the findMinMax() method by providing array numbers with values { 4, 2, 9, 7, 1, 5}. You can modify the numbers array to find the minimum and maximum numbers in a different array. The program initializes min and max variables with the first element of the array. It then iterates over the remaining elements of the array and updates the min and max values if a smaller or larger number is found, respectively. why? 

Output
Minimum number: 1
Maximum number: 9
Java-Programming-Interview-Questions-1 Top 5 Java Programming Interview Questions for Beginners
Top 5 Java Programming Interview

6. Write a Java Program to Find Duplicate Elements in Array

Program 1: Using Brute Force Approach

import java.util.*;

public class DuplicateFinderBruteForce {
    public static void findDuplicates(int[] array) {
        if (array == null || array.length == 0) {
            System.out.println("Array is empty.");
            return;
        }

        System.out.println("Duplicate elements in the array:");

        for (int i = 0; i < array.length - 1; i++) {
            for (int j = i + 1; j < array.length; j++) {
                if (array[i] == array[j]) {
                    System.out.println(array[i]);
                }
            }
        }
    }

    public static void main(String[] args) {
        int[] numbers = { 1, 2, 3, 4, 2, 5, 6, 3, 7, 7 };

        findDuplicates(numbers);
    }
}

In this program, the findDuplicates() method takes an array of integers as input and finds the duplicate elements using a brute-force approach. It iterates through each element and compares it with all subsequent elements to find duplicates. The program demonstrates the usage of the findDuplicates() method by providing an array number with values {1, 2, 3, 4, 2, 5, 6, 3, 7, 7}. You can modify the numbers array to find duplicates in a different array.

Program 2: Using HashSet 

import java.util.*;

public class DuplicateFinderHashSet {
    public static void findDuplicates(int[] array) {
        if (array == null || array.length == 0) {
            System.out.println("Array is empty.");
            return;
        }

        System.out.println("Duplicate elements in the array:");

        Set<Integer> set = new HashSet<>();
        for (int i = 0; i < array.length; i++) {
            if (!set.add(array[i])) {
                System.out.println(array[i]);
            }
        }
    }

    public static void main(String[] args) {
        int[] numbers = { 1, 2, 3, 4, 2, 5, 6, 3, 7, 7 };

        findDuplicates(numbers);
    }
}

In this program, the findDuplicates() method takes an array of integers as input and finds the duplicate elements using a HashSet. It adds each element to the HashSet, and if an element is already present, it is a duplicate.

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The program demonstrates the usage of the findDuplicates() method by providing an array numbers with values {1, 2, 3, 4, 2, 5, 6, 3, 7, 7}. You can modify the numbers array to find duplicates in a different array.

Read more:https://updategadh.com/the-power-of-data-visualization-with-python/

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