Why is import of class not needed when calling method on instance (Java)

Question

Something that\'s confused me - an example:

Thing.java:

import java.util.Date; 

class Thing { 
    static Date getDate() {return new Date();}
}
         


        

Answer 1

import statements are used for couple of things.

1. Compiler type checking and avoid naming collision.
2. Ensures byte code linkage

Whenever we say

System.out.println( new Thing().getDate().getTime() )

The compiler parses this statement left to right and gets into that class.

First level compiler parsing.

1. Go to thing class

2. compile doesn't have any linkage or ClassVersion error from Thing.class

3. Check Thing.class has getDate method.
4. if #3 is good then compiler pointer is still in Thing.class (which has date import statements) and I could invoke Time method.

5. As a consumer TestUsesThing gets only long variable.

   System.out.println( new Thing().getDate() )
   

   5.1 In this case we are implicitly accessing .toString() method