code

In this article we give you another 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

26. Generate Random Number

import java.util.Random;
public class RandomNumber {
    public static void main(String[] args) {
        Random rand = new Random();
        int randomNum = rand.nextInt(100); // Random number between 0 and 99
        System.out.println("Random number: " + randomNum);
    }
}

27. Print a Triangle Pattern

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

28. Simple Calculator Using Switch

import java.util.Scanner;
public class Calculator {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter first number: ");
        int num1 = sc.nextInt();
        System.out.print("Enter second number: ");
        int num2 = sc.nextInt();
        System.out.print("Enter operation (+, -, *, /): ");
        char op = sc.next().charAt(0);
        switch (op) {
            case '+':
                System.out.println("Result: " + (num1 + num2));
                break;
            case '-':
                System.out.println("Result: " + (num1 - num2));
                break;
            case '*':
                System.out.println("Result: " + (num1 * num2));
                break;
            case '/':
                System.out.println("Result: " + (num1 / num2));
                break;
            default:
                System.out.println("Invalid operation");
        }
        sc.close();
    }
}

29. Find Power of a Number

public class PowerOfNumber {
    public static void main(String[] args) {
        int base = 2, exponent = 3;
        int result = 1;
        for (int i = 0; i < exponent; i++) {
            result *= base;
        }
        System.out.println("Result: " + result);
    }
}

30. Find Average of Array Elements

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

31. Count Occurrence of Character in String

public class CountCharacter {
    public static void main(String[] args) {
        String str = "hello world";
        char target = 'l';
        int count = 0;
        for (char c : str.toCharArray()) {
            if (c == target) {
                count++;
            }
        }
        System.out.println("Occurrence of '" + target + "': " + count);
    }
}

32. Check if a String is a Palindrome

public class PalindromeString {
    public static void main(String[] args) {
        String str = "madam";
        String rev = new StringBuilder(str).reverse().toString();
        if (str.equals(rev)) {
            System.out.println(str + " is a palindrome");
        } else {
            System.out.println(str + " is not a palindrome");
        }
    }
}

33. Find Second Largest Number in Array

public class SecondLargest {
    public static void main(String[] args) {
        int[] arr = {1, 2, 3, 4, 5};
        int largest = Integer.MIN_VALUE, secondLargest = Integer.MIN_VALUE;
        for (int num : arr) {
            if (num > largest) {
                secondLargest = largest;
                largest = num;
            } else if (num > secondLargest && num != largest) {
                secondLargest = num;
            }
        }
        System.out.println("Second largest: " + secondLargest);
    }
}

34. Count Occurrence of Word in Sentence

public class WordCount {
    public static void main(String[] args) {
        String sentence = "Java is fun and Java is powerful";
        String word = "Java";
        int count = 0;
        String[] words = sentence.split(" ");
        for (String w : words) {
            if (w.equalsIgnoreCase(word)) {
                count++;
            }
        }
        System.out.println("Occurrence of word '" + word + "': " + count);
    }
}

35. Sum of Elements in a Matrix

public class MatrixSum {
    public static void main(String[] args) {
        int[][] matrix = {
            {1, 2, 3},
            {4, 5, 6},
            {7, 8, 9}
        };
        int sum = 0;
        for (int[] row : matrix) {
            for (int element : row) {
                sum += element;
            }
        }
        System.out.println("Sum of matrix elements: " + sum);
    }
}

36. Transpose of a Matrix

public class TransposeMatrix {
    public static void main(String[] args) {
        int[][] matrix = {
            {1, 2, 3},
            {4, 5, 6}
        };
        int[][] transpose = new int[matrix[0].length][matrix.length];
        for (int i = 0; i < matrix.length; i++) {
            for (int j = 0; j < matrix[i].length; j++) {
                transpose[j][i] = matrix[i][j];
            }
        }
        for (int[] row : transpose) {
            for (int element : row) {
                System.out.print(element + " ");
            }
            System.out.println();
        }
    }
}

37. Count Positive and Negative Numbers in Array

public class CountPositiveNegative {
    public static void main(String[] args) {
        int[] arr = {1, -2, 3, -4, 5};
        int positiveCount = 0, negativeCount = 0;
        for (int num : arr) {
            if (num > 0) {
                positiveCount++;
            } else if (num < 0) {
                negativeCount++;
            }
        }
        System.out.println("Positive numbers: " + positiveCount);
        System.out.println("Negative numbers: " + negativeCount);
    }
}

38. Find Sum of Diagonal Elements in Matrix

public class DiagonalSum {
    public static void main(String[] args) {
        int[][] matrix = {
            {1, 2, 3},
            {4, 5, 6},
            {7, 8, 9}
        };
        int sum = 0;
        for (int i = 0; i < matrix.length; i++) {
            sum += matrix[i][i];
        }
        System.out.println("Sum of diagonal elements: " + sum);
    }
}

39. Find Intersection of Two Arrays

import java.util.HashSet;
public class Intersection {
    public static void main(String[] args) {
        int[] arr1 = {1, 2, 3, 4, 5};
        int[] arr2 = {4, 5, 6, 7, 8};
        HashSet set = new HashSet<>();
        for (int num : arr1) {
            set.add(num);
        }
        System.out.print("Intersection: ");
        for (int num : arr2) {
            if (set.contains(num)) {
                System.out.print(num + " ");
            }
        }
    }
}

40. Find Union of Two Arrays

import java.util.HashSet;
public class Union {
    public static void main(String[] args) {
        int[] arr1 = {1, 2, 3, 4, 5};
        int[] arr2 = {4, 5, 6, 7, 8};
        HashSet set = new HashSet<>();
        for (int num : arr1) {
            set.add(num);
        }
        for (int num : arr2) {
            set.add(num);
        }
        System.out.print("Union: ");
        for (int num : set) {
            System.out.print(num + " ");
        }
    }
}

41. Count Words in a Sentence

public class WordCounter {
    public static void main(String[] args) {
        String sentence = "Java programming is fun";
        String[] words = sentence.split(" ");
        System.out.println("Number of words: " + words.length);
    }
}

42. Check if Two Strings are Anagrams

import java.util.Arrays;
public class AnagramCheck {
    public static void main(String[] args) {
        String str1 = "listen", str2 = "silent";
        char[] arr1 = str1.toCharArray();
        char[] arr2 = str2.toCharArray();
        Arrays.sort(arr1);
        Arrays.sort(arr2);
        if (Arrays.equals(arr1, arr2)) {
            System.out.println(str1 + " and " + str2 + " are anagrams");
        } else {
            System.out.println(str1 + " and " + str2 + " are not anagrams");
        }
    }
}

43. Check if a Matrix is Symmetric

public class SymmetricMatrix {
    public static void main(String[] args) {
        int[][] matrix = {
            {1, 2, 3},
            {2, 4, 5},
            {3, 5, 6}
        };
        boolean isSymmetric = true;
        for (int i = 0; i < matrix.length; i++) {
            for (int j = 0; j < matrix.length; j++) {
                if (matrix[i][j] != matrix[j][i]) {
                    isSymmetric = false;
                    break;
                }
            }
        }
        if (isSymmetric) {
            System.out.println("The matrix is symmetric");
        } else {
            System.out.println("The matrix is not symmetric");
        }
    }
}

44. Find Duplicate Elements in Array

import java.util.HashSet;
public class FindDuplicates {
    public static void main(String[] args) {
        int[] arr = {1, 2, 3, 4, 2, 5, 1};
        HashSet set = new HashSet<>();
        System.out.print("Duplicates: ");
        for (int num : arr) {
            if (!set.add(num)) {
                System.out.print(num + " ");
            }
        }
    }
}

45. Find Substring in String

public class SubstringCheck {
    public static void main(String[] args) {
        String str = "Hello World";
        String sub = "World";
        if (str.contains(sub)) {
            System.out.println(sub + " is a substring of " + str);
        } else {
            System.out.println(sub + " is not a substring of " + str);
        }
    }
}

46. Reverse Words in a Sentence

public class ReverseWords {
    public static void main(String[] args) {
        String sentence = "Java is fun";
        String[] words = sentence.split(" ");
        String reversedSentence = "";
        for (int i = words.length - 1; i >= 0; i--) {
            reversedSentence += words[i] + " ";
        }
        System.out.println("Reversed: " + reversedSentence.trim());
    }
}

47. Convert String to Uppercase

public class StringToUpperCase {
    public static void main(String[] args) {
        String str = "hello";
        String upperStr = str.toUpperCase();
        System.out.println("Uppercase: " + upperStr);
    }
}

48. Find the Sum of Natural Numbers

public class SumOfNaturalNumbers {
    public static void main(String[] args) {
        int num = 10, sum = 0;
        for (int i = 1; i <= num; i++) {
            sum += i;
        }
        System.out.println("Sum: " + sum);
    }
}

49. Remove Duplicates from Array

import java.util.HashSet;
public class RemoveDuplicates {
    public static void main(String[] args) {
        int[] arr = {1, 2, 3, 4, 2, 5, 1};
        HashSet set = new HashSet<>();
        System.out.print("Array without duplicates: ");
        for (int num : arr) {
            if (set.add(num)) {
                System.out.print(num + " ");
            }
        }
    }
}

50. Find the Largest Element in Array

public class LargestElement {
    public static void main(String[] args) {
        int[] arr = {1, 2, 3, 4, 5};
        int largest = arr[0];
        for (int num : arr) {
            if (num > largest) {
                largest = num;
            }
        }
        System.out.println("Largest element: " + largest);
    }
}

These examples touch upon basic programming concepts, string manipulation, array operations, and algorithms that will help you gain a solid understanding of Java fundamentals.

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");
        }
    }
}