Difference between static and non static variables in Java

Hello coders, in this tutorial we will learn the basic types of variables in Java and differentiate between static and non-static variables in Java.

A variable is used to store information that can be used in Java program to perform any task. There are three types of variables in java, and they are as follows:

 1. Local variable

 2. Instance variable

 3. Static variable

1. Local variable: A local variable is a variable that is local to a specific method. In other words, the variable can be used only in the method of the class where it is defined.

2. Instance variable: The variable that is declared in the class and can be used by any method of that class only is called an instance variable. It is instance-specific, which means other classes are not aware of its existence.

3. Static variable: The variable which is declared using the keyword static and shared among all the classes is called a static variable. 

The local variable and the instance variable are non-static variables.
Example of the above-explained types of variables in java:

class Class1{
    int a;//Instance Variable
    public static int b=20;//Static variable
}

public class Demo{
    public void demo1()
    {
        int c=15,res;//Local Variable
        res=c*c;
        System.out.println("Square of Local variable "+ c + " : "+res);
    }
     public static void main(String []args){
         Demo obj=new Demo();
         obj.demo1();
         Class1 ob1=new Class1();
         ob1.a=35;
         System.out.println("Square of Instance variable "+ ob1.a +" : " + ob1.a*ob1.a);
         System.out.println("Square of Static variable "+ Class1.b +" : "+ Class1.b*Class1.b);
     }
}

Output for the above code is:

Square of Local variable 15 : 225 
Square of Instance variable 35 : 1225 
Square of Static variable 20 : 400

In the above code, it is shown the definition and calling the local, instance and static variables in a java program.
In addition, to learn about how to call a non-static function from a static function click here.

The difference between Static and non-static variables in java :

 Static variable

1. A static variable is declared using the static keyword.    
2.  Memory is allocated at the run-time when the class is loaded and only once. However, final keyword can be used to show that the value of a static variable remains the same after initialization.
3. The static as well as non-static methods can access a static variable.
4. A static variable is common to every object of the class.
5. It is like a global variable, available to all.
6. Above all, the class name is used to access the static variable outside the class.

Non-Static variable

1.  A non-static variable is declared as a regular variable.
2.  Memory is allocated when a new object is created. However, each time a new object is created new memory space is allotted which can lead to wastage of memory.
   
3. The static methods cannot use a non-static variable.
   
4. A non-static variable is accessible to its instance(where it is defined).
   
5. It is a local variable and available to object of the class.
6. Accessing a non-static variable is done using the reference to the instance where it is declared.

In conclusion, the article describes the difference between static and non-static variables.

Also read: Difference between super() and this() in Java