What Are Java Variables?

A variable is a container that stores data (like numbers, text, or true/false). Every variable has:

• A datatype
• A name
• A value

Types of Java Variables

1️⃣ Local Variables → Declared within a method, constructor, or block. → Accessible only within that block.

Example:

public class LocalVariableExample {
    public static void main(String[] args) {
        int number = 10; // Local variable
        System.out.println(number);
    }
}

2️⃣ Instance Variables → Declared within a class but outside methods. → Each instance (object) of the class gets its own copy.

Example:

public class InstanceVariableExample {
    // Instance variable
    int number = 20;

    public static void main(String[] args) {
        InstanceVariableExample object = new InstanceVariableExample();
        System.out.println(object.number);
    }
}

3️⃣ Static (Class) Variables → Declared with static. → One copy for all instances of the class. → Accessible with the class name.

Example:

public class StaticVariableExample {
    // Static variable
    static int number = 30;

    public static void main(String[] args) {
        System.out.println(StaticVariableExample.number);
    }
}

Summary

• Local variable — Inside methods or blocks, temporary.
• Instance variable — Inside class, for each object.
• Static (class) variable — Inside class, shared by all instances.