25 simple Java code examples

In this article we give you 25 simple Java code examples that cover various programming concepts like control structures, loops, arrays, methods, and object-oriented programming.

We always find that actually trying out code examples and running them is one of the best ways to learn a new language

1. Hello World

public class HelloWorld {
    public static void main(String[] args) {
        System.out.println("Hello, World!");
    }
}

2. Sum of Two Numbers

public class Sum {
    public static void main(String[] args) {
        int a = 5, b = 10;
        int sum = a + b;
        System.out.println("Sum: " + sum);
    }
}

3. Check Even or Odd

public class EvenOdd {
    public static void main(String[] args) {
        int num = 10;
        if (num % 2 == 0) {
            System.out.println(num + " is even");
        } else {
            System.out.println(num + " is odd");
        }
    }
}

4. Find Largest Number

public class LargestNumber {
    public static void main(String[] args) {
        int a = 5, b = 10, c = 3;
        if (a > b && a > c) {
            System.out.println("Largest is: " + a);
        } else if (b > c) {
            System.out.println("Largest is: " + b);
        } else {
            System.out.println("Largest is: " + c);
        }
    }
}

5. Factorial of a Number

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

6. Fibonacci Series

public class Fibonacci {
    public static void main(String[] args) {
        int a = 0, b = 1, n = 10;
        System.out.print(a + " " + b);
        for (int i = 2; i < n; i++) {
            int next = a + b;
            System.out.print(" " + next);
            a = b;
            b = next;
        }
    }
}

7. Reverse a String

public class ReverseString {
    public static void main(String[] args) {
        String str = "Hello";
        String rev = "";
        for (int i = str.length() - 1; i >= 0; i--) {
            rev += str.charAt(i);
        }
        System.out.println("Reversed: " + rev);
    }
}

8. Prime Number Check

public class PrimeCheck {
    public static void main(String[] args) {
        int num = 29;
        boolean isPrime = true;
        for (int i = 2; i <= num / 2; i++) {
            if (num % i == 0) {
                isPrime = false;
                break;
            }
        }
        if (isPrime) {
            System.out.println(num + " is prime");
        } else {
            System.out.println(num + " is not prime");
        }
    }
}

9. Sum of Array Elements

public class SumArray {
    public static void main(String[] args) {
        int[] arr = {1, 2, 3, 4, 5};
        int sum = 0;
        for (int num : arr) {
            sum += num;
        }
        System.out.println("Sum: " + sum);
    }
}

10. Swap Two Variables

public class Swap {
    public static void main(String[] args) {
        int a = 5, b = 10;
        System.out.println("Before swap: a = " + a + ", b = " + b);
        int temp = a;
        a = b;
        b = temp;
        System.out.println("After swap: a = " + a + ", b = " + b);
    }
}

11. Multiplication Table

public class MultiplicationTable {
    public static void main(String[] args) {
        int num = 5;
        for (int i = 1; i <= 10; i++) {
            System.out.println(num + " x " + i + " = " + num * i);
        }
    }
}

12. Armstrong Number

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

13. Sum of Digits

public class SumOfDigits {
    public static void main(String[] args) {
        int num = 1234, sum = 0;
        while (num != 0) {
            sum += num % 10;
            num /= 10;
        }
        System.out.println("Sum of digits: " + sum);
    }
}

14. Reverse a Number

public class ReverseNumber {
    public static void main(String[] args) {
        int num = 1234, reversed = 0;
        while (num != 0) {
            int digit = num % 10;
            reversed = reversed * 10 + digit;
            num /= 10;
        }
        System.out.println("Reversed: " + reversed);
    }
}

15. GCD of Two Numbers

public class GCD {
    public static void main(String[] args) {
        int a = 54, b = 24;
        while (b != 0) {
            int temp = b;
            b = a % b;
            a = temp;
        }
        System.out.println("GCD: " + a);
    }
}

16. LCM of Two Numbers

public class LCM {
    public static void main(String[] args) {
        int a = 54, b = 24, gcd = 1;
        for (int i = 1; i <= a && i <= b; i++) {
            if (a % i == 0 && b % i == 0) {
                gcd = i;
            }
        }
        int lcm = (a * b) / gcd;
        System.out.println("LCM: " + lcm);
    }
}

17. Leap Year Check

public class LeapYear {
    public static void main(String[] args) {
        int year = 2024;
        if ((year % 4 == 0 && year % 100 != 0) || year % 400 == 0) {
            System.out.println(year + " is a leap year");
        } else {
            System.out.println(year + " is not a leap year");
        }
    }
}

18. Count Vowels in a String

public class VowelCount {
    public static void main(String[] args) {
        String str = "Hello World";
        int count = 0;
        for (char c : str.toCharArray()) {
            if (c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u') {
                count++;
            }
        }
        System.out.println("Vowel count: " + count);
    }
}

19. Find Length of a String

public class StringLength {
    public static void main(String[] args) {
        String str = "Hello World";
        System.out.println("Length: " + str.length());
    }
}

20. Convert Binary to Decimal

public class BinaryToDecimal {
    public static void main(String[] args) {
        String binary = "1010";
        int decimal = Integer.parseInt(binary, 2);
        System.out.println("Decimal: " + decimal);
    }
}

21. Convert Decimal to Binary

public class DecimalToBinary {
    public static void main(String[] args) {
        int decimal = 10;
        String binary = Integer.toBinaryString(decimal);
        System.out.println("Binary: " + binary);
    }
}

22. Find ASCII Value of a Character

public class ASCIIValue {
    public static void main(String[] args) {
        char c = 'A';
        int ascii = (int) c;
        System.out.println("ASCII value: " + ascii);
    }
}

23. Print Numbers from 1 to 10

public class PrintNumbers {
    public static void main(String[] args) {
        for (int i = 1; i <= 10; i++) {
            System.out.println(i);
        }
    }
}

24. Find Minimum and Maximum in an Array

public class MinMaxArray {
    public static void main(String[] args) {
        int[] arr = {1, 2, 3, 4, 5};
        int min = arr[0], max = arr[0];
        for (int num : arr) {
            if (num < min) { min = num; } if (num > max) {
                max = num;
            }
        }
        System.out.println("Min: " + min + ", Max: " + max);
    }
}

25. Check if a Number is Palindrome

public class Palindrome {
    public static void main(String[] args) {
        int num = 121, reversed = 0, original = num;
        while (num != 0) {
            int digit = num % 10;
            reversed = reversed * 10 + digit;
            num /= 10;
        }
        if (original == reversed) {
            System.out.println(original + " is a palindrome");
        } else {
            System.out.println(original + " is not a palindrome");
        }
    }
}

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