15 Java Programs for Beginners

The fastest way to learn Java is to write small programs that each practise one idea. Below are 15 beginner programs with complete, commented code: number checks, loops, strings, and simple algorithms. Type each one out (do not just copy), compile it, and run it. Together they exercise variables, operators, control flow, arrays, and methods — the core skills from the rest of this tutorial cluster.

1. Even or odd

public class EvenOdd {
    public static void main(String[] args) {
        int n = 7;
        // % gives the remainder; an even number divides by 2 with no remainder.
        System.out.println(n % 2 == 0 ? "Even" : "Odd"); // Odd
    }
}

2. Sum of first N numbers

public class SumN {
    public static void main(String[] args) {
        int n = 5, sum = 0;
        for (int i = 1; i <= n; i++) sum += i; // accumulate 1+2+3+4+5
        System.out.println("Sum = " + sum);    // Sum = 15
    }
}

3. Factorial

public class Factorial {
    public static void main(String[] args) {
        int n = 5;
        long fact = 1;                       // use long: factorials grow fast
        for (int i = 2; i <= n; i++) fact *= i;
        System.out.println(n + "! = " + fact); // 120
    }
}

4. Largest of three numbers

public class Largest {
    public static void main(String[] args) {
        int a = 12, b = 27, c = 19;
        int max = Math.max(a, Math.max(b, c)); // Math.max compares two at a time
        System.out.println("Largest = " + max); // 27
    }
}

5. Reverse a number

public class ReverseNumber {
    public static void main(String[] args) {
        int n = 1234, reversed = 0;
        while (n != 0) {
            reversed = reversed * 10 + n % 10; // peel off the last digit
            n /= 10;
        }
        System.out.println(reversed); // 4321
    }
}

6. Palindrome check (string)

public class Palindrome {
    public static void main(String[] args) {
        String s = "level";
        String reversed = new StringBuilder(s).reverse().toString();
        System.out.println(s.equals(reversed) ? "Palindrome" : "Not"); // Palindrome
    }
}

7. Count vowels in a string

public class CountVowels {
    public static void main(String[] args) {
        String s = "Jalgaon";
        int count = 0;
        for (char ch : s.toLowerCase().toCharArray()) {
            if ("aeiou".indexOf(ch) >= 0) count++; // is the char a vowel?
        }
        System.out.println("Vowels = " + count); // 3
    }
}

8. Prime number check

public class PrimeCheck {
    public static void main(String[] args) {
        int n = 29;
        boolean prime = n > 1;
        for (int i = 2; i * i <= n; i++) { // check up to the square root
            if (n % i == 0) { prime = false; break; }
        }
        System.out.println(prime ? "Prime" : "Not prime"); // Prime
    }
}

9. Fibonacci series

public class Fibonacci {
    public static void main(String[] args) {
        int a = 0, b = 1;
        System.out.print(a + " " + b);
        for (int i = 2; i < 8; i++) {
            int next = a + b;          // each term is the sum of the previous two
            System.out.print(" " + next);
            a = b; b = next;
        }
        // 0 1 1 2 3 5 8 13
    }
}

10. Multiplication table

public class Table {
    public static void main(String[] args) {
        int n = 7;
        for (int i = 1; i <= 10; i++) {
            System.out.println(n + " x " + i + " = " + (n * i));
        }
    }
}

11. Swap two numbers (without a temp variable)

public class Swap {
    public static void main(String[] args) {
        int a = 5, b = 9;
        a = a + b; // a = 14
        b = a - b; // b = 5
        a = a - b; // a = 9
        System.out.println("a=" + a + ", b=" + b); // a=9, b=5
    }
}

12. Array sum and average

public class ArrayStats {
    public static void main(String[] args) {
        int[] marks = {88, 92, 75, 60};
        int sum = 0;
        for (int m : marks) sum += m;
        System.out.println("Average = " + (double) sum / marks.length); // 78.75
    }
}

13. Find the maximum in an array

public class ArrayMax {
    public static void main(String[] args) {
        int[] data = {12, 45, 7, 89, 33};
        int max = data[0];
        for (int v : data) if (v > max) max = v; // keep the biggest seen so far
        System.out.println("Max = " + max); // 89
    }
}

14. FizzBuzz

public class FizzBuzz {
    public static void main(String[] args) {
        for (int i = 1; i <= 15; i++) {
            if (i % 15 == 0) System.out.println("FizzBuzz");
            else if (i % 3 == 0) System.out.println("Fizz");
            else if (i % 5 == 0) System.out.println("Buzz");
            else System.out.println(i);
        }
    }
}

15. Simple calculator with a method

public class Calculator {
    // A reusable method that returns a result.
    static double apply(double a, double b, char op) {
        return switch (op) {           // modern switch expression
            case '+' -> a + b;
            case '-' -> a - b;
            case '*' -> a * b;
            case '/' -> b != 0 ? a / b : Double.NaN; // guard against divide-by-zero
            default  -> Double.NaN;
        };
    }
    public static void main(String[] args) {
        System.out.println(apply(6, 3, '*')); // 18.0
        System.out.println(apply(6, 0, '/')); // NaN
    }
}

Common mistakes

• Copying without typing. You learn by typing and fixing your own errors, not by pasting.
• Integer division surprises. In program 12, casting to double is what makes the average correct.
• Wrong loop bounds. Decide whether you want < or <=; an off-by-one error is the most common bug here.
• Comparing Strings with ==. In the palindrome program, use .equals(), never ==.
• Skipping the divide-by-zero guard. Program 15 checks b != 0 for a reason.

FAQ

What should I practise after these? Re-solve each one a second way — for example, write factorial recursively, or read the input from the keyboard with a Scanner.

How do I run these? Save each in a file matching the class name (e.g. Factorial.java), then javac Factorial.java and java Factorial. See the JDK setup guide.

Keep going

Strengthen the fundamentals behind these programs with Control Flow in Java and Arrays in Java. All tutorials are on the Java hub; for guided practice in Jalgaon, see the Java course.

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