Category: React • Beginner
Published on 04 Mar 2026
Explanation
Write a Java program to reverse a string without using built-in reverse functions.
Code Example
public class ReverseString {
public static void main(String[] args) {
String str = "Java";
String reversed = "";
for (int i = str.length() - 1; i >= 0; i--) {
reversed += str.charAt(i);
}
System.out.println(reversed);
}
}
Explanation
Write a Java program to calculate the factorial of a number using a loop.
Code Example
public class Factorial {
public static void main(String[] args) {
int n = 5;
int fact = 1;
for (int i = 1; i <= n; i++) {
fact *= i;
}
System.out.println(fact);
}
}
Explanation
Write a Java program to check whether a given number is prime.
Code Example
public class PrimeNumber {
public static void main(String[] args) {
int num = 7;
boolean isPrime = true;
for (int i = 2; i <= num / 2; i++) {
if (num % i == 0) {
isPrime = false;
break;
}
}
System.out.println(isPrime ? "Prime" : "Not Prime");
}
}
Explanation
Write a Java program to print the Fibonacci series up to n terms.
Code Example
public class Fibonacci {
public static void main(String[] args) {
int n = 10, a = 0, b = 1;
System.out.print(a + " " + b + " ");
for (int i = 2; i < n; i++) {
int c = a + b;
System.out.print(c + " ");
a = b;
b = c;
}
}
}
Explanation
Write a Java program to count the frequency of each character in a string using HashMap.
Code Example
import java.util.HashMap;
public class CharacterCount {
public static void main(String[] args) {
String str = "hello";
HashMap<Character, Integer> map = new HashMap<>();
for (char c : str.toCharArray()) {
map.put(c, map.getOrDefault(c, 0) + 1);
}
System.out.println(map);
}
}