The difference between regular (non-static) and static methods

Java is a Object Oriented Programming(OOP) language, which means we need objects to access methods and variables inside of a class. However this is not always true. While discussing static keyword in java, we learned that static members are class level and can be accessed directly without any instance. In this article we will see the difference between static and non-static methods.

Static Method Example

class StaticDemo
{
   public static void copyArg(String str1, String str2)
   {
       //copies argument 2 to arg1
       str2 = str1;
       System.out.println("First String arg is: "+str1);
       System.out.println("Second String arg is: "+str2);
   }
   public static void main(String agrs[])
   {
      /* This statement can also be written like this: 
       * StaticDemo.copyArg("XYZ", "ABC");
       */
      copyArg("XYZ", "ABC");
   }
}

Output:

First String arg is: XYZ
Second String arg is: XYZ

As you can see in the above example that for calling static method, I didn’t use any object. It can be accessed directly or by using class name as mentioned in the comments.

Non-static method example

class JavaExample
{
   public void display()
   {
       System.out.println("non-static method");
   }
   public static void main(String agrs[])
   {
	   JavaExample obj=new JavaExample();
	   /* If you try to access it directly like this:
	    * display() then you will get compilation error
	    */
       obj.display();
   }
}

Output:

non-static method

A non-static method is always accessed using the object of class as shown in the above example.

Notes:
How to call static methods: direct or using class name:

StaticDemo.copyArg(s1, s2);
OR copyArg(s1, s2);

How to call a non-static method: using object of the class:

JavaExample obj = new JavaExample();

Important Points:

1. Static Methods can access static variables without any objects, however non-static methods and non-static variables can only be accessed using objects.
2. Static methods can be accessed directly in static and non-static methods. For example the static public static void main() method can access the other static methods directly. Also a non-static regular method can access static methods directly.