Closed 2 days ago.

I’ve been using Spark Java framework in which data can be retrieved from a session like this, without any explicit type cast:

I was referring to this article.

I have some code maintaining a map of proto enums to their fully qualified descriptor names like so:

I have the following code

I was trying to run the below code

I have a concrete type (“B”) which is a subtype of several other types (“A1”, “A2” in the example below), and I want to create a method that possibly returns the supertype, or B. So essentially I want to require that B is a subtype of my generic parameter. A code example might make it clearer:

I am wondering why am I getting this compilation error :

This question already has answers here: Generic wildcard types should not be used in return parameters (3 answers) Closed 2 days ago. Having this: public <T extends DataAgent> DataProcessor<? extends DataAgent> resolveProcessor( final String response, T dAgent) throws Exception { if (dAgent.getType() == RESULT_TYPE.INLINE) { return InlineParser.parse(response, (InlineDataAgent) dAgent); } return DefaultParser.parse(response, (DefaultDataAgent) dAgent); } […]

I have many interfaces (Foo and Bar), abstract classes implementing those interfaces (AbstractFoo and AbstractBar), and classes extending those abstract classes (FooImpl1, FooImpl2, BarImpl1 and BarImpl2). The interfaces are generics and parameters are pointing each others. Everything is compiling until I use a method from a generic field in the constructor of AbstractBar class (this.foo.addBar(this);).