Java Program to check the accessibility of an Instance Variable by a Static Method

In Java, the static methods are defined using static keywords but to declare instance variables we don't use static keywords. Generally, we can't access the instance variable by a static method.

In this article, we will create an instance variable and then we will check the accessibility of that instance variable by a static method. Let's understand static method and instance variable first.

Java Instance Variable

In the context of programming language, variables are the name of containers that contain data of any type. We can say it is a storage unit. A variable can be initialized at the time of declaration or we can initialize it when required in the whole program. But value must be of the same data type as specified at the time of declaration.

Instance variables are one of the types of variables that are non-static. They are declared inside class but outside of every method scope of that class. They are accessible to all methods that belong to the class where it is defined. They can be public, private, protected, or default. If we don't mention any access specifier then variable will be initialized with default access specifier.

Java Static Method

Static methods are defined using a non access modifier keyword called static. Normally, we call a method by creating an object of its class but static methods can be called without using objects. We call them using their class name only because static method belongs to class not to the instance of that class.

To call Static Method:

Class_name.static_method_name

Example: Use of static Method

Most of the members of inbuilt class Math is static. We can use them directly without creating its object. In the following Java program, we will use static methods ceil() and floor() of Math class.

public class Main {
   public static void main( String[] args ) {
      double x = 6.55;
      double y = 4.32;
      System.out.println(" Ceil value of x: " + Math.ceil(x) );
      System.out.println(" Floor value of y: " + Math.floor(y) );
      System.out.println(" Value of PI = " + Math.PI);
   }
}

Output:

Ceil value of x: 7.0
Floor value of y: 4.0
Value of PI = 3.141592653589793

Accessibility of an Instance Variable by Static Method

We already mentioned earlier in this article that we can't access instance variables by a static method directly, we can only access them by creating an instance or object of the class.

Example: Error in Accessing Instance Variable

The following program demonstrates whether we can access instance variable by static method main() or not.

public class Main {
   public String str = "Tutorialspoint"; 
   public static void main(String []args) {
      System.out.println(" Accessing instance variable " + str);
   }
}

If you try to run the above code you will get an error:

Main.java:4: error: non-static variable str cannot be referenced from a static context
   System.out.println(" Accessing instance variable " + str);
                                                        ^
1 error

Example: Accessing Instance Variable

The following program illustrates how we can access an instance variable by a static method. We will create an object of the Main class and by using this object we can access the variable ?str'.

public class Main {
   public String str = "Tutorialspoint"; 
   public static void main(String []args) {
      Main obj = new Main(); 
      // creating object using new keyword
      // To access the instance variable 'str'
      System.out.println(" Accessing instance variable: " + obj.str);
   }
}

Output:

Accessing instance variable: Tutorialspoint

Conclusion

In this article, we have understood the concept of instance variable and static method. Also, we discussed the accessibility of instance variable by a static method through the java programs.