Java_Local&Global_Variable

• In Java, variables are classified based on where they are declared and where they can be accessed.

Local Variable:

• A local variable is declared inside a method, constructor, or block.
• Declared inside { } of a method or block.
• Accessible only inside that method/block.
• Must be initialized before use
• Lifetime exists only while 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)

• In Java, there is no true global variable like in C/C++.
  Instead, we use:

  1)Instance Variable (Non-static)
  2)Static Variable (Class variable)
  These are commonly called "global variables".

1) Instance Variable:

• Declared inside class but outside methods.
• Accessible by all methods of the class.
• Each object gets its own copy.
• Gets default value (0, null, false).

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();
    }
}

2)Static Variable(Class Variable)

• Declared using static keyword.
• Shared among all objects.
• Accessed using class name.

class Demo {
    static int z = 30;  // static variable
    public static void main(String[] args) {
        System.out.println("Value of z: " + Demo.z);
    }
}