Intro to Java Methods – Write Once, Use Many Times

 Tired of repeating the same code again and again? Methods to the rescue! They let you wrap code in a reusable block.

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🧱 What is a Method?

A method is a mini-program inside your program. It does a specific task.

Example:

public static void sayHello() {

    System.out.println("Hello, world!");

}

▶️ Calling a Method

Once defined, you can use it like this:

sayHello();

// in your main method

Math.random() in Java

 

Get Whole Numbers

You can use it to get random integers too:

int num = (int)(Math.random() * 10); // 0 to 9

Mini Challenge: Dice Game

Write a program that:

• Rolls two dice

• Adds them together

• Prints “You rolled: X + Y = Z”

Introduction to Java Arrays

 

In Java, an array lets you store multiple values in a single variable. Super useful when you’re working with a list of items!

//Structure of arrays in java

int[] numbers = {10, 20, 30, 40};

//Accessing Elements

System.out.println(numbers[0]); // 10

System.out.println(numbers[2]); // 30

💥 Array Properties

• Fixed size (you can’t change its length)

• Index starts at 0

• numbers.length gives you the number of elements

🧪 Challenge

Create an array of your 5 favorite numbers and print them all using a loop.

Loops in Java: Meet the While Loop

 

Loops in Java: Meet the While Loop

In Java, loops are used to repeat a block of code as long as a certain condition is true. One of the simplest types of loops is the while loop.

The Syntax

while (condition) {

    // code to repeat

}

As long as the condition is true, the code inside the loop keeps running.

If-Else Explained (JAVA)

 

What if your program needs to make choices? Like checking if someone is old enough to vote, or if a number is positive or negative?

That’s where if-else statements come in — they let your code decide what to do based on a condition.

//Basic If-Else Structure

if (condition) {

    // do this if condition is true

} else {

    // do this if condition is false

}

//Example 1 : Even or Odd

int number = 7;

if (number % 2 == 0) {

    System.out.println("The number is even.");

} 

else {

    System.out.println("The number is odd.");

}

Taking User Input in Java (with Scanner)

 

🧪 Step 1: Import the Scanner

Before using it, you need to import it at the top of your code:

import java.util.Scanner;


✏️ Example: Asking for a Name
import java.util.Scanner;

public class InputExample {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);  // Create Scanner

        System.out.print("What's your name? ");
        String name = input.nextLine();  // Read a line of text

        System.out.println("Hello, " + name + "!");
    }
}

Understanding Variables and Data Types in Java

 

🧠 What Is a Variable?

Think of a variable as a container that stores data. It could be a number, a word, or even a true/false value.

Common Data Types In Java

Data Type            Example                    What it stores
int                        int age = 15;              Whole Numbers

double                 double d = 1.2;          Decimal Numbers

String                  String s = "TOM";     Text(Always in quotes)

boolean               boolean i = true;         True or False

char                     char grade = 'A';         A single character(in single quotes)

//Sample Code

public class VariableDemo {

    public static void main(String[] args) {

        int age = 15;

        double score = 95.5;

        String name = "Aarav";

        boolean isCool = true;

        char grade = 'A';

        System.out.println("Name: " + name);

        System.out.println("Age: " + age);

        System.out.println("Score: " + score);

        System.out.println("Cool? " + isCool);

        System.out.println("Grade: " + grade);

    }

}

//output

Name: Aarav  

Age: 15  

Score: 95.5  

Cool? true  

Grade: A  

Getting Started with Java: First Program (Hello, World!)

 

🧠 What Is "Hello, World!"?

It's a basic program that does one thing: prints the message Hello, World! to the screen. But more importantly, it introduces you to the structure of a Java program.

//Code

public class HelloWorld

{

    public static void main(String[] args)

    {

          System.out.println("Hello World!");

     }

}

🛠 How to Run It

1. Open a code editor (like VS Code or just Notepad).

2. Save the file as HelloWorld.java.

3. Open Command Prompt (or Terminal).

Why I Started Learning CS?

My interest in CS started with curiosity. I always wondered how apps, websites, and games were made. Once I began learning Java in AP Computer Science A, I realized how powerful and creative coding really is. It’s like solving puzzles but with endless possibilities.

Through CS with Aarav, I’ll share what I learn, the projects I build, and the tips I wish I knew earlier. Whether you're just starting out or curious about CS, I hope this blog helps you in your journey too!

Let’s code something awesome.