Difference Between Global Variable And Local Variable?

Today we discuss about the difference between the global and local variable.First we talk about the Local Variable

1.LOCAL VARIABLE :

• Declared inside a method, constructor, or block

• Exists only while that method/block runs

• JVM does NOT give default values

• Lives in stack memory

Example:

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

2.GLOBAL VARIABLE :

A) Instance Variable (Object-level):

• Declared inside class but outside methods

• Each object gets its own copy

• Stored in heap memory

• Has default values

Example:

class Student {
    int age;   // instance variable
}
Student s1 = new Student();
System.out.println(s1.age); // prints 0

B) Static Variable (Closest to real global):

• Declared using static

• Single shared copy for the entire class

• Loaded once when class is loaded

Example:

class College {
    static String name = "ABC College";
}
System.out.println(College.name);

Key facts:

• Shared across all objects

• Accessible using class name

• Misuse leads to tight coupling & bugs