Can you implement an abstract class

Abstract classes are similar to interfaces. You cannot instantiate them, and they may contain a mix of methods declared with or without an implementation. However, with abstract classes, you can declare fields that are not static and final, and define public, protected, and private concrete methods.

With interfaces, all fields are automatically public, static, and final, and all methods that you declare or define as default methods are public. In addition, you can extend only one class, whether or not it is abstract, whereas you can implement any number of interfaces.

By reading this list of interfaces, you can infer that an instance of HashMap regardless of the developer or company who implemented the class can be cloned, is serializable which means that it can be converted into a byte stream; see the section Serializable Objects , and has the functionality of a map.

Note that many software libraries use both abstract classes and interfaces; the HashMap class implements several interfaces and also extends the abstract class AbstractMap.

In an object-oriented drawing application, you can draw circles, rectangles, lines, Bezier curves, and many other graphic objects. These objects all have certain states for example: position, orientation, line color, fill color and behaviors for example: moveTo, rotate, resize, draw in common. March 6, at am. Ketul Chauhan says:. July 18, at am. Pulkit Sharma says:. July 30, at am.

March 11, at am. Bhagyashri Chaudhari says:. March 2, at am. Frank says:. March 12, at pm. March 15, at pm. Deepak gupta says:. September 23, at pm. Kenneth says:. February 17, at pm. Praveen says:. September 23, at am. VIJAY says:. February 6, at am. Morteza says:. September 16, at am. Alwin says:. September 14, at am. August 23, at am. May 12, at am. February 25, at am. March 6, at pm. Fravashi Kaustav says:. February 10, at pm. Deepak Tiwari says:. June 2, at pm. James says:. August 26, at am.

August 27, at am. Yoganathan says:. June 19, at pm. June 20, at am. Siva says:. August 18, at am. In this example, the class DerivedClass is derived from an abstract class BaseClass. The abstract class contains an abstract method, AbstractMethod , and two abstract properties, X and Y.

In the preceding example, if you attempt to instantiate the abstract class by using a statement like this:. You will get an error saying that the compiler cannot create an instance of the abstract class 'BaseClass'. For more information, see the C Language Specification. The language specification is the definitive source for C syntax and usage.

Feedback will be sent to Microsoft: By pressing the submit button, your feedback will be used to improve Microsoft products and services. Privacy policy. Just one more time, in the simplest terms possible: An Interface is like a protocol. It doesn't designate the behavior of the object; it designates how your code tells that object to act. An interface would be like the English Language: defining an interface defines how your code communicates with any object implementing that interface.

An interface is always an agreement or a promise. When a class says "I implement interface Y", it is saying "I promise to have the same public methods that any object with interface Y has". On the other hand, an Abstract Class is like a partially built class. It is much like a document with blanks to fill in.

It might be using English, but that isn't as important as the fact that some of the document is already written. An abstract class is the foundation for another object.

When a class says "I extend abstract class Y", it is saying "I use some methods or properties already defined in this other class named Y". The interface is an agreement to have a specific set of public methods for your class. You would have your class extend an abstract class if you or someone else wrote a class that already had some methods written that you want to use in your new class.

These concepts, while easy to confuse, are specifically different and distinct. For all intents and purposes, if you're the only user of any of your classes, you don't need to implement interfaces. Here's an example that helped me with understanding abstract classes. It's just a very simple way of explaining it in my opinion. It tastes like an apple.

Now I give you a fruit. Well, it doesn't make much sense, so you shouldn't be able to do that. This is accomplished by making the Fruit class abstract as well as the eat method inside of it.

Also, a note. An abstract class is just like an interface, but you can define methods in an abstract class whereas in an interface they are all abstract.

Abstraction and interfaces are two very different tools.