3.1 Declaring and Initializing Variables: In Java, variables are used to store and manipulate data.

Let's learn how to declare and initialize variables using a simple example:

public class VariablesExample {
    public static void main(String[] args) {
        // Declaring variables
        int age;
        double height;
        boolean isStudent;

        // Initializing variables
        age = 25;
        height = 1.75;
        isStudent = true;

        // Printing variable values
        System.out.println("Age: " + age);
        System.out.println("Height: " + height);
        System.out.println("Is Student: " + isStudent);
    }
}

• In this example, we declare three variables: age of type int, height of type double, and isStudent of type boolean. We then initialize these variables with specific values.
• To access the value stored in a variable, we can use the variable's name. In this case, we print the values of the variables using the System.out.println() statement.

3.2 Primitive Data Types:

Java provides several primitive data types to store different kinds of information.

Here are a few commonly used ones:

• int: Used to store whole numbers, such as 42 or -10.
• double: Used to store decimal numbers, such as 3.14 or -2.5.
• boolean: Used to store either true or false.
• char: Used to store a single character, such as 'a' or '$'.

Here's an example that demonstrates the usage of these primitive data types:

public class PrimitiveDataTypesExample {
    public static void main(String[] args) {
        int age = 25;
        double height = 1.75;
        boolean isStudent = true;
        char grade = 'A';

        System.out.println("Age: " + age);
        System.out.println("Height: " + height);
        System.out.println("Is Student: " + isStudent);
        System.out.println("Grade: " + grade);
    }
}

• In this example, we declare and initialize variables of different primitive data types and print their values.