static method and instance method

What is the difference between static method and instance method?

Instance method or simply method is a class member which needs its reference, so as to be used someplace else
Static methods are methods that do need reference to be used.

A very common example is the method main which you have been using all this while. So before anythings loads it is important that the main is called first. Since it is static and does not rely on a reference, it can do so.

and for example when I create a class, can I just call the method by static method

Whenever you need to use an instance method outside of its scope you need to refer it through the classes' instance.

class A {
           public void hello() {
          // some code
           }
}

public class MainClass {
       A a = new A(); // here a is an instance of class A
       a.hello(); // to access hello method inside A we need to refer it via its reference variable
  }

Now when I add static to a method what it means is that you do not need to create a reference variable to refer it in some other class.

class A {
           static void hello() {
          // some code
           }
}

public class MainClass {
      hello(); //no need to create a reference variable of the class
  }

However, there are some rules when applying static to a method

• they can only call other static methods
• they cannot use this and super keywords
• and can only access static data

Hope this helps! Ask again if you require.