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Java interface vs abstract classes9/1/2023 ![]() ![]() ![]() Abstract Classes can be useful for containing protected and private methods as well as variables. You need to have private or protected methods and variables. ![]() There is a need to use non-static and non-final values inside a class so that an object can modify these variables.The child classes can redefine each of these abstract methods separately. An abstract class would contain all the abstract methods. Your application has some code that needs to be shared amongst different classes.When should you use Java Abstract Classes? You want a child class to implement all abstract methods in the interface.You are more concerned with the behavior of the class rather than who is implementing the behavior.You want to implement multiple inheritance in Java.You can also achieve loose coupling with the help of interfaces.You can separate the definition of a method from its inheritance hierarchy with the help of interfaces.You can resolve methods dynamically at runtime with the help of interfaces.You can achieve 100% abstraction with the help of interfaces in Java.With the help of abstract classes you can define a common interface for your subclasses.Abstract classes allow you to reuse code.You can specify a particular template for future specific classes.You can offer default functionality with the help of abstract classes.Programmers from team get intention that they are free to implement another interface besides given one in abstract class.Īlso, they can write their own methods (private or public) into the abstract class, if they think it is required during implementation of sub classes i.e. Now you pass these contracts in an abstract class as below. and implement rendering and user input.All development team understand easily that they must just implement and do nothing extra. Creates rendering window, initializes OpenGL the rendering process and handling user input: // Abstract class for an OpenGL app. and then you can derive from this class and implement custom code for e.g. You can define an abstract class that initializes OpenGL, sets up the window environment, etc. Think for example of an infrastructure for an OpenGL application. Instead, I'd use an abstract class when I want to provide some default infrastructure code and behavior, and make it possible to client code to derive from this abstract class, overriding the pure virtual methods with some custom code, and complete this behavior with custom code. We can run an abstract class if it has main(). Classes that implement this interface will provide some concrete behavior themselves. Abstract classes can extend other class and implement interfaces but interface can only extend other interfaces. I'd use an interface if I want to define a set of rules using which a component can be programmed, without specifying a concrete particular behavior. Moreover, when you want to build DLL's with a C++ object-oriented interface (instead of pure C DLL's), as described in this article, it's better to export interfaces (the "mature approach") instead of C++ classes (this is basically what COM does, but without the burden of COM infrastructure). In other words, with interfaces you have high decoupling between client code and server code. build a COM component in C++ and use it in Visual Basic, or build a COM component in C and use it in C++, or build a COM component with Visual C++ version X and use it with Visual C++ version Y. This helps defining an ABI (Application Binary Interface) that makes it possible to e.g. In fact, a COM component exports only interfaces (i.e. In Windows programming, interfaces are fundamental in COM. Virtual void Method4() = 0 // make MyAbstractClass not instantiable Without much knowledge of the details, I would assume that theoretically, abstract methods dispatch faster as long as the language doesnt implement multiple inheritance for classes. Empty virtual destructor for proper cleanup Basically, both interface methods and abstract methods make use of dynamic dispatching, so the difference is minimal if there is any at all. without any code), instead with abstract class you mean a C++ class with virtual methods that can be overridden, and some code, but at least one pure virtual method that makes the class not instantiable. Of course not to mention, you may only extend one class in java in where you may implement number of interfaces. abstract class implementing an interface interface including another interface Being new to java, I really would appreciate if anyone could exactly pinpoint the leverage/advantage of one over the other in specific situations. Abstract classes more agile than interfaces. I assume that with interface you mean a C++ class with only pure virtual methods (i.e. You may force subclasses to implement some must-have functionalities with abstract methods (those without implementations). ![]()
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