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1. Reverse a String
public class ReverseString { public static void main(String[] args) { String str = "Automation"; StringBuilder reversed = new StringBuilder(str).reverse(); System.out.println(reversed); } }
2. Check for Palindrome
public class Palindrome { public static void main(String[] args) { String str = "madam"; String reversed = new StringBuilder(str).reverse().toString(); System.out.println(str.equals(reversed)); } }
3. Fibonacci Series
public class Fibonacci { public static void main(String[] args) { int n = 10, num1 = 0, num2 = 1; System.out.print("Fibonacci Series: " + num1 + ", " + num2); for (int i = 2; i < n; i++) { int num3 = num1 + num2; System.out.print(", " + num3); num1 = num2; num2 = num3; } }
4. Factorial of a Number
public class Factorial { public static void main(String[] args) { int num = 5, factorial = 1; for (int i = 1; i <= num; i++) { factorial *= i; } System.out.println(factorial); } }
5. Prime Number Check
public class PrimeCheck { public static void main(String[] args) { int num = 11; boolean isPrime = true; for (int i = 2; i <= Math.sqrt(num); i++) { if (num % i == 0) { isPrime = false; break; } } System.out.println(isPrime); } }
6. Count Vowels and Consonants
public class VowelConsonantCount { public static void main(String[] args) { String str = "Automation";
System.out.println(Arrays.toString(merged)); } }
9. Find the Largest Element in an Array
public class LargestInArray { public static void main(String[] args) { int[] arr = {1, 3, 5, 7, 9}; int largest = arr[0]; for (int num : arr) { if (num > largest) { largest = num; } } System.out.println(largest); } }
10. Remove Duplicates from an Array
import java.util.HashSet; public class RemoveDuplicates { public static void main(String[] args) { int[] arr = {1, 2, 2, 3, 4, 4}; HashSet set = new HashSet<>(); for (int num : arr) { set.add(num); } System.out.println(set); } }
11. Check if a Number is Armstrong
public class ArmstrongNumber { public static void main(String[] args) { int num = 153, sum = 0, temp = num; while (temp != 0) { int digit = temp % 10; sum += Math.pow(digit, 3); temp /= 10; } System.out.println(num == sum); } }
12. Reverse a Number
public class ReverseNumber { public static void main(String[] args) { int num = 12345, reversed = 0; while (num != 0) { reversed = reversed * 10 + num % 10; num /= 10; } System.out.println(reversed); } }
13. Calculate GCD of Two Numbers
public class GCD { public static void main(String[] args) { int a = 60, b = 48; while (b != 0) { int temp = b;
int start = 10, end = 50; for (int num = start; num <= end; num++) { boolean isPrime = true; for (int i = 2; i <= Math.sqrt(num); i++) { if (num % i == 0) { isPrime = false; break; } } if (isPrime && num > 1) { System.out.print(num + " "); } } } }
17. Find the Second Largest Element in an Array
public class SecondLargest { public static void main(String[] args) { int[] arr = {12, 35, 1, 10, 34, 1}; int first = Integer.MIN_VALUE, second = Integer.MIN_VALUE; for (int num : arr) { if (num > first) { second = first; first = num; } else if (num > second && num != first) { second = num; } } System.out.println(second); }
18. Swap Two Numbers
public class SwapNumbers { public static void main(String[] args) { int a = 5, b = 10; a = a + b; b = a - b; a = a - b; System.out.println("a: " + a + ", b: " + b); } }
19. Print the Pascal's Triangle
public class PascalsTriangle { public static void main(String[] args) { int rows = 5; for (int i = 0; i < rows; i++) { int num = 1; System.out.format("%" + (rows - i) * 2 + "s", ""); for (int j = 0; j <= i; j++) { System.out.format("%4d", num); num = num * (i - j) / (j + 1); } System.out.println(); } } }
20. Find the Missing Number in an Array
public class MissingNumber { public static void main(String[] args) {
23. Implementing a Simple Calculator
import java.util.Scanner; public class SimpleCalculator { public static void main(String[] args) { Scanner scanner = new Scanner(System.in); System.out.print("Enter first number: "); double num1 = scanner.nextDouble(); System.out.print("Enter second number: "); double num2 = scanner.nextDouble(); System.out.print("Enter operation (+, - , , /): "); char operation = scanner.next().charAt(0); double result; switch (operation) { case '+': result = num1 + num2; break; case '-': result = num1 - num2; break; case '': result = num1 * num2; break; case '/': result = num1 / num2; break; default: throw new IllegalArgumentException("Invalid operation"); } System.out.println("Result: " + result); } }
24. Find the Sum of Digits of a Number
public class SumOfDigits { public static void main(String[] args) { int num = 12345, sum = 0; while (num != 0) { sum += num % 10; num /= 10; }
System.out.println(sum); } }
25. Find the Length of a String
public class StringLength { public static void main(String[] args) { String str = "Automation"; System.out.println(str.length()); } }
26. Check if a String is Empty
public class CheckEmptyString { public static void main(String[] args) { String str = ""; System.out.println(str.isEmpty()); } }
27. Count the Occurrences of a Character in a String
public class CountCharacter { public static void main(String[] args) { String str = "Automation"; char ch = 'a'; int count = 0; for (char c : str.toCharArray()) { if (c == ch) count++; } System.out.println(count); } }
public static void main(String[] args) { int[] arr1 = {1, 2, 3, 4}; int[] arr2 = {3, 4, 5, 6}; HashSet set = new HashSet<>(); for (int num : arr1) { set.add(num); } for (int num : arr2) { if (set.contains(num)) { System.out.print(num + " "); } } } }
31. Find the Factorial of a Number using Recursion
public class FactorialRecursion { public static void main(String[] args) { int num = 5; System.out.println(factorial(num)); } static int factorial(int n) { if (n == 0) return 1; return n * factorial(n - 1); } }
32. Generate Random Numbers
import java.util.Random; public class RandomNumbers {
public static void main(String[] args) { Random random = new Random(); for (int i = 0; i < 5; i++) { System.out.println(random.nextInt(100)); // Random number between 0- 99 } } }
33. Check if a Year is Leap Year
public class LeapYear { public static void main(String[] args) { int year = 2024; boolean isLeap = (year % 4 == 0 && year % 100 != 0) || (year % 400 == 0); System.out.println(isLeap); } }
34. Find the Sum of First N Natural Numbers
public class SumOfNaturalNumbers { public static void main(String[] args) { int n = 10, sum = n * (n + 1) / 2; System.out.println(sum); } }
35. Implement a Simple Login System
import java.util.Scanner; public class SimpleLogin { public static void main(String[] args) { String username = "admin"; String password = "password"; Scanner scanner = new Scanner(System.in);
int maxCount = 0; for (char c : charCount.keySet()) { if (charCount.get(c) > maxCount) { maxCount = charCount.get(c); maxChar = c; } } System.out.println(maxChar); } }
38. Implementing Bubble Sort
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; } } } for (int num : arr) { System.out.print(num + " "); } } }
39. Implementing Selection Sort
public class SelectionSort { public static void main(String[] args) { int[] arr = {64, 25, 12, 22, 11}; int n = arr.length; for (int i = 0; i < n - 1; i++) { int minIndex = i; for (int j = i + 1; j < n; j++) { if (arr[j] < arr[minIndex]) { minIndex = j; } } int temp = arr[minIndex]; arr[minIndex] = arr[i]; arr[i] = temp; } for (int num : arr) { System.out.print(num + " "); } } }
