How to avoid unchecked cast warnings with Java Generics

Question

Somehow my old question was closed, so I open a new one:

I am using Java Generics to implement a generic bidirectional Hash Map out of an SQL Query. It should be abl

Answer 1

You can use the following annotation to make the compiler not output those warnings:

@SuppressWarnings("unchecked")

See this related question which deals with the same issue. The answer there will explain everything you need to know.

Answer 2

If you are using the Spring Framework, you can use CastUtils:

import static org.springframework.data.util.CastUtils.cast;

obj.setString(cast(someObject));
String bob = cast(someObject);

Answer 3

You're getting warnings because what you're doing can't be proved to be safe. You're assuming that getInstance(colTypeL) will return an Extractor<L> - but that can't be verified at either compile-time or execution time.

You can use @SuppressWarnings("unchecked") as mentioned by others, but I would try to rethink the design somewhat.