I’m trying to create a functional interface in Java with a single method (of course) that can take any type of parameter(s) and return any data type (i.e. a generic method). This is what I have so far: Calculator.java Main.java The error says: bad operand types for binary operator ‘+’ Is it …
Tag: interface
How can I create a stream of objects?
Let’s say I have: and Then in a service, I have: It is not allowed to do the following: But ultimately, I have other classes that would share this interface and would want to do: Is there a way around this? Like using flatMap? (I noticed that if I have a wrapper class on a List of SomeClass objects, I
How to present abstract class which has relationship with interface class in class diagram
I have to do diagram with minimum of one abstract class and interface.I though to be a good idea to implement the interface class here. My table is customer which is the abstract class.The interface …
Why would you declare a variable of type X within the interface X in Java?
I ran into the following code recently: It is confusing to me what the purpose of this could be. Can someone explain why someone would write this code? Answer Every field in an interface is implicitly static, so this isn’t defining something that lives in every Filter — it’s defining one com…
access interface out of the class java
I have a class A, another is B, there is one interface Ai with one method ok() only. Class A implements Ai, inside the ok I’m printing just a line. Class B has an instance of A, I want to access A’s interface Ai inside B. Can it be done ? If so how ? Answer All I needed is
Is it better practice to use static factory methods over an interface implemented by many different objects? [closed]
Closed. This question is opinion-based. It is not currently accepting answers. Want to improve this question? Update the question so it can be answered with facts and citations by editing this post. Closed 3 years ago. Improve this question It seems as though you could either use static factory methods or you…
How to implement interface in-line instead of using a class in Dart/Flutter?
Is there any way to implement an interface in dart/flutter without having to use a class? Currently, how I implement it is with the code below However, I would like to implement these interface methods without having to use a class, just as I would in java. Something that would look like the code below. Answe…
Android MVP – Calls the server
I started to learn MVP but I have a few questions related the communication between the Model and the Presenter, for example a login feature Activity will get all the fields, send to the presenter, the presenter will validate and if it’s everything as expected the presenter will call the model to send t…
Java strange class cast exception
Could anyone help me understand why in 1 situation I do not have ClassCastException? At least String::trim is not a MagicFunction. Answer So, method references (like String::trim) are a bit weird; unlike most expressions in Java, they don’t really have a type of their own. Something like this: won’…
What is the purpose of a static method in interface from Java 8?
Why are static methods supported from Java 8? What is the difference between the two lines in main method in below code? As we can see above, I is not even implemented in B. What purpose would it serve to have a static method in an interface when we can write the same static method in another class and call