Java Variables

Java variables are named storage locations used to store data values. Here's an overview:

Declaration and Initialization:

• Variables are declared using keywords like int, double, boolean, etc.
• They can be initialized with values during or after declaration.

Variable Names:

• Must start with a letter, underscore (_), or dollar sign ($).
• Subsequent characters can be letters, digits (0-9), underscores, or dollar signs.
• Case-sensitive: age and Age are different variables.

Types of Variables:

• Local Variables: Defined within methods, constructors, or blocks.
• Instance Variables: Belong to instances of a class (objects) and are declared in the class but outside methods.
• Class Variables (Static Variables): Belong to the class and are shared among all instances of the class.

Variable Scope:

• Local variables have method scope and are accessible only within the method or block where they are declared.
• Instance variables have object scope and are accessible throughout the class.
• Class variables have class scope and are shared among all instances of the class.

Example

public class VariablesExample {
    // Class variable
    static int count = 0;

    public static void main(String[] args) {
        // Local variable
        int age = 25;

        // Instance variables
        String name = "Darling";
        double salary = 1000.50;

        System.out.println("Name: " + name);
        System.out.println("Age: " + age);
        System.out.println("Salary: " + salary);

        // Increment class variable
        count++;
        System.out.println("Count: " + count);
    }
}

Summary

Java variables are essential for storing and manipulating data in programs. Understanding variable types, scope, and naming conventions is crucial for writing efficient and maintainable Java code.