Java 8 permits static interface methods With Java 8, interfaces can have static methods. They can also have concrete instance methods, but not instance fields. There are really two questions here: Why, in the bad old days, couldn’t interfaces contain static methods? Why can’t static methods be overridden? Static methods in interfaces There was no … Read more
Using interfaces over concrete types is the key for good encapsulation and for loose coupling your code. It’s even a good idea to follow this practice when writing your own APIs. If you do, you’ll find later that it’s easier to add unit tests to your code (using Mocking techniques), and to change the underlying … Read more
2019 Update The current answers and the official documentation are outdated. And for those new to TypeScript, the terminology used isn’t clear without examples. Below is a list of up-to-date differences. 1. Objects / Functions Both can be used to describe the shape of an object or a function signature. But the syntax differs. Interface … Read more
I wrote an article about that: Abstract classes and interfaces Summarizing: When we talk about abstract classes we are defining characteristics of an object type; specifying what an object is. When we talk about an interface and define capabilities that we promise to provide, we are talking about establishing a contract about what the object … Read more
Scanning for classes is not easy with pure Java. The spring framework offers a class called ClassPathScanningCandidateComponentProvider that can do what you need. The following example would find all subclasses of MyClass in the package org.example.package ClassPathScanningCandidateComponentProvider provider = new ClassPathScanningCandidateComponentProvider(false); provider.addIncludeFilter(new AssignableTypeFilter(MyClass.class)); // scan in org.example.package Set<BeanDefinition> components = provider.findCandidateComponents(“org/example/package”); for (BeanDefinition component : … Read more
To expand on the answer by bradtgmurray, you may want to make one exception to the pure virtual method list of your interface by adding a virtual destructor. This allows you to pass pointer ownership to another party without exposing the concrete derived class. The destructor doesn’t have to do anything, because the interface doesn’t … Read more
Consider just using composition instead of trying to simulate Multiple Inheritance. You can use Interfaces to define what classes make up the composition, eg: ISteerable implies a property of type SteeringWheel, IBrakable implies a property of type BrakePedal, etc. Once you’ve done that, you could use the Extension Methods feature added to C# 3.0 to … Read more
Since Java 8 there is a Function<T, R> interface (docs), which has method R apply(T t); You can use it to pass functions as parameters to other functions. T is the input type of the function, R is the return type. In your example you need to pass a function that takes Component type as … Read more
Almost always List is preferred over ArrayList because, for instance, List can be translated into a LinkedList without affecting the rest of the codebase. If one used ArrayList instead of List, it’s hard to change the ArrayList implementation into a LinkedList one because ArrayList specific methods have been used in the codebase that would also … Read more
What is the difference between an interface and abstract class?