I have 2 classes as below :: And I have a method in a service class : Now I need to pass ItemA or ItemB based upon some conditions in the caller. The return type doesn’t change in either case. How I can do that using generics or wild cards. This is what I am trying to achieve : Is
Tag: wildcard
How to use Hibernate Search with a wildcard query and output the result object list
I want to search for a string in XML data in MySQL database using hibernate search and print the result list of data that contains the string. Answer ..it worked
Use Class as a method signature
In the method signature, I need a parameter that is any class type that extends from Collection (List, Set, etc), so I can return any of them. To try to achieve this I did use the following method: However when I try to use it like: The following error arises: I did search for an answer already solved in Stac…
Messages not consumed when using wildcard queues in ActiveMQ Artemis
If I create queues on ActiveMQ Artemis test.A and a wildcard queue test.# then I can send a message to test.A and it will also be delivered to test.#. However, I am surprised to learn that when I consume the message from test.# then the message is still present on test.A How can I change my code or configurat…
Does it matter if function returns T or object if T can not be inferred from context?
I found the following source code in gson: public T fromJson(Reader json, Type typeOfT) throws JsonIOException, JsonSyntaxException { JsonReader jsonReader = newJsonReader(json); T …
How to resolve `Raw use of parameterized class ‘Comparable’` warning?
Got to implement the method below for an assignment which it’s subject is “WildCards”, but don’t know where to use wildcards in order to resolve the warning. Any ideas ? Answer Comparable is a generic interface, so to use it safely you must always specify the generic type to use. In yo…
Wildcard not allowed for Iterable in Java
I have following code setup. But this is not allowed as wildcard is not allowed for Iterable. What actually Java tries to a achieve here by not allowing this? What modifications would get this working? Answer When a class instance is created, it invokes the initializer of the super type. But you can’t u…
Why HashMap with generic declaration ” does not accept value “new Object()” in the put method?
While working on interview questions, I have come across below code: The above two put method’s are throwing compile time error. But, when I add m.put(3, new ArrayList()); it is adding to map with no compile time error. It is very clear for me that I can add new Object() as a value in HashMap because of…
Java Generics With Any Type
I’m trying to write a method in Java that will be able to add a custom Key object to an array, or change an already existing key in the array if there is one. However, I can’t seem to get it to work. The types that keys will use are primarily be String and Integer, but my universal approach doesn&…