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System.out.println( ( (A) b ).fi ); What is this, upcasting?

flex567 wrote: ↑

Sun Jun 24, 2018 6:14 am

System.out.println( ( (A) b ).fi ); What is this, upcasting?

Yes, because you are casting a reference of a subtype to a supertype.
Try this if you are not clear - https://stackoverflow.com/questions/234 ... t-to-class

I think I understand:

A a = new B(); //upcasting

B b = new B();
a = (A) b;//also upcasting
(A) b;//also upcasting

There is no cast in A a = new b(); ! Also it should new B() not new b.

It is implicit upcast.

This is implicit "widening" not implicit upcast. There is nothing like implicit or explicit cast. Only cast. Cast is done using the cast operator i.e. ( ). If there is no cast operator, there is no cast.

http://www.baeldung.com/java-type-casting

This is that particular author's view. You can take it up with him/her. There is no such term as implicit or explicit cast in the Java language specification. The term implicit cast or explicit cast is nonsensical. Either there is a cast or there is not. There is widening and widening can be explicit (i.e. using a cast) or implicit (i.e. without use a cast).

By the way, the book you quoted seems to be about Spring so I don't think the author is paying too much attention about such small technicality that has nothing to do with spring.

-Paul.

I noticed it on other pages as well.

You can talk to the author or ask someone else if you are not satisfied. Our view on this is quite clear.

HTH,
Paul.

This discussion has nothing to do with the exam so I am splitting it into a separate topic.