Another 25 simple Java code examples

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

Table of Contents

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.

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