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.