ICSE Class 10 Computer Applications: Java Programs — Most Important — Important Questions with Answers 2026

Short Answer Questions (2-3 Marks)

• Q: Write a Java program to check whether a number is prime or not.
  Ans: ```java import java.util.Scanner; public class PrimeCheck { public static void main(String[] args) { Scanner sc = new Scanner(System.in); System.out.print("Enter a number: "); int n = sc.nextInt(); boolean isPrime = true; if (n <= 1) isPrime = false; else { for (int i = 2; i <= Math.sqrt(n); i++) { if (n % i == 0) { isPrime = false; break; } } } System.out.println(n + (isPrime ? " is prime" : " is not prime")); } } ``` Key concept: Check divisibility only up to √n for efficiency.
• Q: Write a Java program to find the sum of digits of a number.
  Ans: ```java import java.util.Scanner; public class SumDigits { public static void main(String[] args) { Scanner sc = new Scanner(System.in); System.out.print("Enter number: "); int n = sc.nextInt(); int sum = 0, temp = n; while (temp > 0) { sum += temp % 10; temp /= 10; } System.out.println("Sum of digits of " + n + " = " + sum); } } ``` Logic: Extract last digit using %10, remove it using /10, repeat until number becomes 0.
• Q: Write a Java program to check if a string is a palindrome.
  Ans: ```java import java.util.Scanner; public class Palindrome { public static void main(String[] args) { Scanner sc = new Scanner(System.in); System.out.print("Enter string: "); String s = sc.nextLine(); String rev = new StringBuilder(s).reverse().toString(); if (s.equalsIgnoreCase(rev)) System.out.println(s + " is a palindrome"); else System.out.println(s + " is not a palindrome"); } } ``` Alternative: Compare characters from both ends using a loop.

Long Answer / Application Questions (4-6 Marks)

• Q: Write a Java program to find the largest and smallest elements in an array.
  Ans: ```java import java.util.Scanner; public class MinMax { public static void main(String[] args) { Scanner sc = new Scanner(System.in); System.out.print("Enter size: "); int n = sc.nextInt(); int[] arr = new int[n]; System.out.println("Enter elements:"); for (int i = 0; i < n; i++) arr[i] = sc.nextInt(); int max = arr[0], min = arr[0]; for (int i = 1; i < n; i++) { if (arr[i] > max) max = arr[i]; if (arr[i] < min) min = arr[i]; } System.out.println("Largest: " + max + ", Smallest: " + min); } } ```
• Q: Write a Java program to sort an array using Bubble Sort.
  Ans: ```java public class BubbleSort { public static void main(String[] args) { int[] arr = {64, 34, 25, 12, 22, 11, 90}; int n = arr.length; for (int i = 0; i < n-1; i++) { for (int j = 0; j < n-i-1; j++) { if (arr[j] > arr[j+1]) { int temp = arr[j]; arr[j] = arr[j+1]; arr[j+1] = temp; } } } System.out.print("Sorted: "); for (int x : arr) System.out.print(x + " "); } } ``` Time complexity: O(n²). Compare adjacent elements and swap if out of order.

Exam Tips for This Chapter

• Revise all definitions and laws from Java Programs — Most Important — they are commonly asked as 1-2 mark questions
• Practice diagrams related to Java Programs — Most Important — neat labelled diagrams carry 2-3 marks
• For numericals, always show formula → substitution → answer with correct units
• Previous year analysis shows Java Programs — Most Important carries 8-12 marks in the board exam