Mohamad mhana

Posted on Sep 13

3 Java Mini Programs to Try Today!

#java #coding #programming #challenge

Looking to practice Java hands-on and strengthen your coding skills? Here are three small programs, broken into three chunks each, with clear explanations and key skills highlighted.

1️⃣ Simple Calculator

What it does: Perform addition, subtraction, multiplication, and division between two numbers.

Chunk 1 – Input from the User

Scanner sc = new Scanner(System.in);

System.out.print("Enter first number: ");
double num1 = sc.nextDouble();

System.out.print("Enter operator (+, -, *, /): ");
char operator = sc.next().charAt(0);

System.out.print("Enter second number: ");
double num2 = sc.nextDouble();

Explanation: This chunk takes two numbers and an operator from the user. It prepares the program to perform calculations based on user input.

This enforces: Handling user input and understanding data types in Java.

Chunk 2 – Calculate the Result


double result;

switch(operator) {
    case '+': result = num1 + num2; break;
    case '-': result = num1 - num2; break;
    case '*': result = num1 * num2; break;
    case '/': 
        if(num2 != 0) result = num1 / num2; 
        else { System.out.println("Cannot divide by zero!"); return; }
        break;
    default: System.out.println("Invalid operator"); return;
}

Explanation: This chunk decides which arithmetic operation to perform using a switch statement. It also handles invalid input and division by zero.

This enforces: Conditional logic and basic arithmetic operations.

Chunk 3 – Display the Result

System.out.println("Result: " + result);

Explanation: This final chunk prints the calculated result to the console so the user can see it.

This enforces: Output handling and program completion.

💡 Try this: Modify it to handle multiple operations in a row.

Switch Statements in Java - GeeksforGeeks

2️⃣ Number Guessing Game

What it does: Guess a randomly generated number between 1–100.

Chunk 1 – Setup

Scanner sc = new Scanner(System.in);
Random rand = new Random();
int number = rand.nextInt(100) + 1;
int guess = 0;

System.out.println("Guess a number between 1 and 100:");

Explanation: This chunk initializes the program, generates a random number, and prepares to take guesses from the user.

This enforces: Random number generation, variable initialization, and console setup.

Chunk 2 – Loop Through Guesses

while(guess != number) {
    guess = sc.nextInt();
    if(guess < number) System.out.println("Too low! Try again:");
    else if(guess > number) System.out.println("Too high! Try again:");

Explanation: This chunk repeatedly asks the user for guesses until the correct number is entered, providing hints for each attempt.

This enforces: Loops and conditional branching for interactive programs.

Chunk 3 – Correct Guess

    else System.out.println("🎉 Congrats! You guessed it!");
}

Explanation: Once the user guesses correctly, the program prints a congratulatory message and ends.

This enforces: Program termination handling and proper feedback to the user.

💡 Try this: Limit the number of attempts and show a “Game Over” message.

Random Number in Java

3️⃣ Palindrome Checker

What it does: Checks whether a word or number reads the same forwards and backwards.

Chunk 1 – Take Input

Scanner sc = new Scanner(System.in);
System.out.print("Enter a string: ");
String str = sc.nextLine();
String reversed = "";

Explanation: This chunk takes a string input from the user and initializes a variable for the reversed version of the string.

This enforces: String handling and preparing variables for processing.

Chunk 2 – Reverse the String

for(int i = str.length() - 1; i >= 0; i--) {
    reversed += str.charAt(i);
}

Explanation: This chunk reverses the string by looping backwards through each character.

This enforces: Loops and string manipulation skills.

Chunk 3 – Compare and Output

if(str.equalsIgnoreCase(reversed))
    System.out.println("✅ " + str + " is a palindrome!");
else
    System.out.println("❌ " + str + " is not a palindrome.");

Explanation: This final chunk compares the original and reversed strings to determine if the input is a palindrome, then prints the result.

This enforces: Conditional checks, logic building, and output formatting.

💡 Try this: Ignore spaces, punctuation, and capitalization to make it more robust.

Palindrome Program in Java

🎯 Why Try Mini Programs?