Question

Object aThing = new Integer(25);

According to my text book, the expression (Integer) aThing casts the type of the object referenced by aThing(type Object) to type Integer. The casting operation will succeed only if the object referenced by aThing is, in fact type Integer; if not, a ClassCastException will be thown

I don’t understand what the bolded sentence is saying. Can you briefly elaborate on that?

what is the “object referenced by aThing“?

Answer 1

Object aThing = new Integer(25);

Now since aThing reference points to an Integer object. So, you can cast that reference to an Integer. Because an integer reference can point to an Integer object.

Integer intRef = (Integer)aThing; // Ok, `aThing` points to an Integer object

But when you try to typecast that reference to a String reference, then you will get ClassCastException because, a String is not an Integer, and hence cannot contain a reference to an Integer object.

// Exception. A String reference cannot point to `Integer` object
String strRef = (String)aThing;