Hi I am having problems with Generic Types and warning that I get from IDE. I have class that holds generic type value: I have abstract class: and class that extends it: IDE is giving me warning: unchecked overriding return type requires unchecked conversion. What I am missing? Answer This is not the promise …
Tag: generics
Why compiler cannot infer generic types of the inner class in Java?
When the above code snippet is compiled, it leads to Compile-Time error saying “incompatible types: cannot infer type arguments for A.InnerA<>. It seems to me that the Compiler should be able to infer the types to be InnerA<String>. Why is it not able to do so? It would be helpful if someone…
How do I create a constructor for a class that is inheriting from an abstract class with generics?
My university professor shared this class with us (it’s essentially a generic parser using Gson): I created a class that inherits from it so I can read a Business from a file: Intellij automatically generated a constructor for it, but I don’t understand it. Why does the constructor has a class as …
error: constructor in class cannot be applied to given types; with matrix of generic variable in Java
In a first file I declared the Matrix class with corresponding generic variable and with a constructor defined as follows: And in a second test file class with main program I declare the matrix of generic variables with String elements. Nevertheless I don´t quite understand why I get the error: If I´m using a…
Java Generics – argument type and casting
I have a generics problem I am trying to resolve. I’m doing some manual casting and it feels like I’m doing something wrong. I’m a bit new to using generics, so it’s very much possible I am misusing …
Can Functional Interfaces with generic type be stored in a static map?
I have used a static map to store a series of Functional Interfaces which associated with three classes A, B and C all inherited from a parent class. The code runs smoothly as follow: However, there is a warning “Raw use of parameterized class ‘BiConsumer’” on the usage of Biconsumer in the …
How to capture and propagate a wildcard type argument?
I have a couple of classes having identical methods, except with respect to certain parameter types: Now I’m trying to have a main class that stores a mixed list of these class objects and for each of these instances, passes info between its two methods: The List<ICls<?>> and Map<String, …
ClassCastException “Parent cannot be cast to class…are in unnamed module of loader ‘app’ ” with Java Generics and inheritance
I´m currently facing a problem with generics in Java. I need to return a parent instance casted to the child. The sample below shows what I´m trying to achieve. This code does not run through and produces this exception instead: class com.generics.GenericTest$Parent cannot be cast to class com.generics.Generi…
How to use one type in method?
I have two forms, one form to create user and one to update user.These forms are similiar and I want to use one type in my method,I wouldn’t like to create two methods one to create user from registerForm and second to create user from updateForm Answer Use generic method like this: Output:
How to create a type specific Comparator for a flexible type array?
I am stuck in the middle of ‘generic-type-qualifier-land’ and can’t find the right combination of type qualifiers. I have a class that represents a flexible array that can have a number of different types in it. The class holds an ArrayList<Object> as the container for the elements. Th…