super keyword without extends to the super class

Question

There is a code of simple program. In constructor, super() is called without extends to the super class, I can not understand what will does this in this situat

Answer 1

Every class that doesn't explicitly extend another class implicitly extends java.lang.Object. So super() simply calls the no-arg constructor of Object.

Note that this explicit call is unnecessary since the compiler would add it for you. You only need to add a super() call in a constructor when you want to invoke a superclass constructor with arguments.