In this article, we will explore a collection of basic Java programs that serve as an excellent starting point for beginners. By grasping these fundamentals, aspiring programmers can lay a strong foundation for their Java journey.
Swapping of Two Numbers
This is one of the very basic java programs, where we use a temporary variable to swap two numbers.
Java Code
public class NumberSwapper {
public static void main(String[] args) {
int num1 = 10;
int num2 = 20;
System.out.println("Before swapping: num1 = " + num1 + ", num2 = " + num2);
swapNumbers(num1, num2);
System.out.println("After swapping: num1 = " + num1 + ", num2 = " + num2);
}
public static void swapNumbers(int a, int b) {
int temp = a;
a = b;
b = temp;
}
}
Output
Before swapping: num1 = 10, num2 = 20
After swapping: num1 = 10, num2 = 20check whether a word is a palindrome or not
Java Code
public class PalindromeChecker {
public static void main(String[] args) {
String word = "radar";
boolean isPalindrome = checkPalindrome(word);
System.out.println("Is \"" + word + "\" a palindrome? " + isPalindrome);
}
public static boolean checkPalindrome(String word) {
int length = word.length();
for (int i = 0; i < length / 2; i++) {
if (word.charAt(i) != word.charAt(length - i - 1)) {
return false;
}
}
return true;
}
}
Output
Is "radar" a palindrome? true
Find Factorial(n!) of a given number(n)
Java Code
public class Factorial {
public static void main(String[] args) {
int number = 5;
int factorial = calculateFactorial(number);
System.out.println("Factorial of " + number + ": " + factorial);
}
public static int calculateFactorial(int number) {
if (number == 0) {
return 1;
} else {
return number * calculateFactorial(number - 1);
}
}
}
Output
Factorial of 5: 120
Find if the input number is Prime
Java Code
public class PrimeNumberChecker {
public static void main(String[] args) {
int number = 13;
boolean isPrime = checkPrime(number);
System.out.println(number + " is a prime number? " + isPrime);
}
public static boolean checkPrime(int number) {
if (number <= 1) {
return false;
}
for (int i = 2; i <= Math.sqrt(number); i++) {
if (number % i == 0) {
return false;
}
}
return true;
}
}
Output
13 is a prime number? true
Print Fibonacci Series
Java Code
public class FibonacciSeries {
public static void main(String[] args) {
int limit = 10;
System.out.print("Fibonacci Series: ");
int firstTerm = 0;
int secondTerm = 1;
System.out.print(firstTerm + ", " + secondTerm);
for (int i = 2; i < limit; i++) {
int nextTerm = firstTerm + secondTerm;
System.out.print(", " + nextTerm);
firstTerm = secondTerm;
secondTerm = nextTerm;
}
}
}
Output
Fibonacci Series: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34
Check this Generate Fibonacci Series in Java: Top 4 different ways
Checking Armstrong Number
Java Code
public class ArmstrongNumberChecker {
public static void main(String[] args) {
int number = 153;
boolean isArmstrong = checkArmstrong(number);
System.out.println(number + " is an Armstrong number? " + isArmstrong);
}
public static boolean checkArmstrong(int number) {
int originalNumber = number;
int result = 0;
while (number != 0) {
int remainder = number % 10;
result += Math.pow(remainder, 3);
number /= 10;
}
return result == originalNumber;
}
}
Output
153 is an Armstrong number? trueCheck this Armstrong Number in Java: Top 4 Simple ways
Find largest Number in an Array
Java Code
public class LargestNumber {
public static void main(String[] args) {
int[] numbers = {10, 5, 20, 8, 15};
int largestNumber = findLargestNumber(numbers);
System.out.println("Largest number: " + largestNumber);
}
public static int findLargestNumber(int[] numbers) {
int max = numbers[0];
for (int i = 1; i < numbers.length; i++) {
if (numbers[i] > max) {
max = numbers[i];
}
}
return max;
}
}
Output
Largest number: 20Find Smallest Number in an Array
Java Code
public class SmallestNumber {
public static void main(String[] args) {
int[] numbers = {10, 5, 20, 8, 15};
int smallestNumber = findSmallestNumber(numbers);
System.out.println("Smallest number: " + smallestNumber);
}
public static int findSmallestNumber(int[] numbers) {
int min = numbers[0];
for (int i = 1; i < numbers.length; i++) {
if (numbers[i] < min) {
min = numbers[i];
}
}
return min;
}
}
Output
Smallest number: 5Check if two Strings are Anagram
Java Code
public class AnagramChecker {
public static void main(String[] args) {
String str1 = "listen";
String str2 = "silent";
boolean isAnagram = checkAnagram(str1, str2);
System.out.println(str1 + " and " + str2 + " are anagrams? " + isAnagram);
}
public static boolean checkAnagram(String str1, String str2) {
if (str1.length() != str2.length()) {
return false;
}
int[] count = new int[26];
for (int i = 0; i < str1.length(); i++) {
count[str1.charAt(i) - 'a']++;
count[str2.charAt(i) - 'a']--;
}
for (int c : count) {
if (c != 0) {
return false;
}
}
return true;
}
}
Output
listen and silent are anagrams? trueFind Unique Characters in the String
Java Code
public class UniqueCharacters {
public static void main(String[] args) {
String word = "hello";
String uniqueChars = findUniqueCharacters(word);
System.out.println("Unique characters: " + uniqueChars);
}
public static String findUniqueCharacters(String word) {
StringBuilder unique = new StringBuilder();
for (int i = 0; i < word.length(); i++) {
char ch = word.charAt(i);
if (unique.indexOf(String.valueOf(ch)) == -1) {
unique.append(ch);
}
}
return unique.toString();
}
}
Output
Unique characters: heloFind Duplicate Characters in a String
Java Code
public class DuplicateCharacters {
public static void main(String[] args) {
String word = "hello";
String duplicateChars = findDuplicateCharacters(word);
System.out.println("Duplicate characters: " + duplicateChars);
}
public static String findDuplicateCharacters(String word) {
StringBuilder duplicates = new StringBuilder();
StringBuilder allChars = new StringBuilder();
for (int i = 0; i < word.length(); i++) {
char ch = word.charAt(i);
if (allChars.indexOf(String.valueOf(ch)) == -1) {
allChars.append(ch);
} else if (duplicates.indexOf(String.valueOf(ch)) == -1) {
duplicates.append(ch);
}
}
return duplicates.toString();
}
}
Output
Duplicate characters: lReverse a String in Java
Java Code
public class StringReverser {
public static void main(String[] args) {
String word = "hello";
String reversed = reverseString(word);
System.out.println("Reversed string: " + reversed);
}
public static String reverseString(String word) {
StringBuilder reversed = new StringBuilder();
for (int i = word.length() - 1; i >= 0; i--) {
reversed.append(word.charAt(i));
}
return reversed.toString();
}
}
Output
Reversed string: ollehGenerate Random Number in Java
Java Code
import java.util.Random;
public class RandomNumberGenerator {
public static void main(String[] args) {
int randomNum = generateRandomNumber();
System.out.println("Random number: " + randomNum);
}
public static int generateRandomNumber() {
Random random = new Random();
return random.nextInt();
}
}
Output
Random number: 1541134490Find Number of Words Separated by Space in a String
Java Code
public class WordCount {
public static void main(String[] args) {
String sentence = "This is a sample sentence";
int wordCount = countWords(sentence);
System.out.println("Number of words: " + wordCount);
}
public static int countWords(String sentence) {
String[] words = sentence.split(" ");
return words.length;
}
}
Output
Number of words: 5Check Leap Year
Java Code
import java.util.Scanner;
public class LeapYearChecker {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.print("Enter a year: ");
int year = scanner.nextInt();
scanner.close();
if (isLeapYear(year)) {
System.out.println(year + " is a leap year.");
} else {
System.out.println(year + " is not a leap year.");
}
}
public static boolean isLeapYear(int year) {
if (year % 4 == 0) {
if (year % 100 == 0) {
if (year % 400 == 0) {
return true;
} else {
return false;
}
} else {
return true;
}
} else {
return false;
}
}
}
Output
Enter a year: 2010
2010 is not a leap year.More Java Programs
For more basic and advanced Programs Check this Top Java Programs asked in Interviews
Conclusion: Basic Java Programs
In conclusion, this article has explored a collection of 15 basic Java programs that serve as building blocks for establishing a strong foundation in Java programming.Mastering these basic Java programs lays the groundwork for tackling more complex coding tasks and exploring advanced Java topics.
As beginners become more comfortable with these basic java programs, they can gradually explore more advanced Java concepts, algorithms, data structures, and frameworks.