AAP-1.A Represent a value with a variable

What is a Variable?

A variable in programming is like a storage box in your computer's memory where you can keep a piece of information. This information can be a number, text, or other types of data. Variables help you manage and manipulate data in your programs.

Imagine you have a locker at school. You can store your books, stationery, and other items in it. You can label your locker with your name so you know it's yours. Similarly, in Java, you label your storage box with a variable name so you can easily access the stored information.

How to Declare a Variable in Java

In Java, you need to tell the computer two things when you create a variable:

  1. The type of data it will store (like a number or text).

  2. The name of the variable.

Here's the basic syntax:

type variableName;

For example:

int age; // Declares a variable named 'age' that will store an integer
String name; // Declares a variable named 'name' that will store text

Assigning Values to Variables

Once you have declared a variable, you can store information in it using the assignment operator =.

For example:

age = 16; // Assigns the value 16 to the variable 'age'
name = "Alice"; // Assigns the text "Alice" to the variable 'name'

You can also declare and assign a value in one step:

int age = 16;
String name = "Alice";

Example: Using Variables in a Program

Let's look at a simple example of using variables in a Java program.

public class Main {
    public static void main(String[] args) {
        // Declaring and assigning values to variables
        int age = 16;
        String name = "Alice";

        // Using the variables
        System.out.println("Name: " + name);
        System.out.println("Age: " + age);
    }
}

 In this program, we declared two variables, age and name, and assigned values to them. Then, we printed these values using System.out.println.

Real-World Example: Storing a Book's Information

Imagine you are creating a program for a library to store information about books. You can use variables to store the book's title, author, and the number of pages.

public class Book {
    public static void main(String[] args) {
        // Declaring variables for book information
        String title = "To Kill a Mockingbird";
        String author = "Harper Lee";
        int pages = 281;

        // Displaying the book information
        System.out.println("Book Title: " + title);
        System.out.println("Author: " + author);
        System.out.println("Number of Pages: " + pages);
    }
}

Here, we declared variables to store the title, author, and number of pages of a book, and then displayed this information.

Programming Problem

Now it's your turn! Write a Java program that stores information about a student, including their name, age, grade, and favorite subject. Then, display this information in the console.

// Your task:
// 1. Declare variables for name, age, grade, and favorite subject.
// 2. Assign values to these variables.
// 3. Print the information to the console.

public class Student {
    public static void main(String[] args) {
        // Your code here
    }
}

Summary