Java_Local&Global_Variable

Source: Dev.to

Local Variable

• Declared inside a method, constructor, or block ({}).
• Accessible only within that method or block.
• Must be initialized before use.
• Lifetime exists only while the method executes.

class Demo {
    void show() {
        int x = 10; // local variable
        System.out.println("Value of x: " + x);
    }

    public static void main(String[] args) {
        Demo obj = new Demo();
        obj.show();
    }
}

Global Variable (Instance Variable in Java)

Java does not have true global variables like C/C++. Instead, variables declared at the class level serve similar purposes.

Instance Variable (Non‑static)

• Declared inside a class but outside any method.
• Accessible by all methods of the class.
• Each object gets its own copy.
• Receives a default value (0, null, false, etc.) if not explicitly initialized.

class Demo {
    int y = 20; // instance variable

    void display() {
        System.out.println("Value of y: " + y);
    }

    public static void main(String[] args) {
        Demo obj = new Demo();
        obj.display();
    }
}

Static Variable (Class Variable)

• Declared with the static keyword.
• Shared among all instances of the class.
• Typically accessed using the class name.

class Demo {
    static int z = 30; // static variable

    public static void main(String[] args) {
        System.out.println("Value of z: " + Demo.z);
    }
}