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Question about Generics in Java (Super vs. Extends).?
I m reading Absolute Java 6e by Walter Savitch for reference.
Let s say that SomeClass is a class and SomeInt is a interface.
In Ch14.2, Savitch says how...
<T extends SomeClass> would only allow class types that are of or descendants of SomeClass . And <T extends SomeInt> would only allow classes that have implemented SomeInt correctly.
In chap 16.1, Savitch states that "To specify that the wildcard type be an ancestor type of some class or interface, use super rather than extends .".
I m confused here. It sounds like extends and super accomplishes the same thing in this context. What is the difference?
1 Answer
- ChrisLv 74 years ago
No, an ancestor of class T doesn't extend T, but T extends the ancestor.
You use "extends" for subclasses, and "super" for ancestors, i.e. superclasses.
See here: https://stackoverflow.com/questions/2827585/what-i...
