Differences between Interfaces and Abstract Classes

Q

What's the difference between an interface and an abstract class?

✍: FYIcenter

A

An abstract class may contain code in method bodies, which is not allowed in an interface. With abstract classes, you have to inherit your class from it and Java does not allow multiple inheritance. On the other hand, you can implement multiple interfaces in your class.

Interfaces provide a form of multiple inheritance. A class can extend only one other class. Interfaces are limited to public methods and constants with no implementation.

Abstract classes can have a partial implementation, protected parts, static methods, etc. A Class may implement several interfaces. But in case of abstract class, a class may extend only one abstract class.

Interfaces are slow as it requires extra indirection to to find corresponding method in in the actual class. Abstract classes are fast.

Neither Abstract classe or Interface can be instantiated.

2007-03-03, 6174👍, 0💬

System.setOut() - Setting Standard Console Output to
How could Java classes direct program messages to the system console, but error messages, say to a file? The class System has a variable out that represents the standard output, and the variable err that represents the standard error device. By default, they both connected to the system console. But... 2007-03-03, 9048👍, 0💬

System.loadLibrary() - Loading DLL for JNI Interface
An application needs to load a library before it starts to run, how to code? One option is to use a static block to load a library before anything is called. For example, class Test { static { System.loadLibrary("myApp.dll" );} .... } When you call new Test(), the static block will be called first b... 2007-03-03, 9013👍, 0💬

Clone of Map Objects
Jack developed a program by using a Map container to hold key/value pairs. He wanted to make a change to the map. He decided to make a clone of the map in order to save the original data on side. What do you think of it? If Jack made a clone of the map, any changes to the clone or the original map w... 2007-03-03, 7765👍, 0💬

Runable Interface and Thread
What is more advisable to create a thread, by implementing a Runnable interface or by extending Thread class? Strategically speaking, threads created by implementing Runnable interface are more advisable. If you create a thread by extending a thread class, you cannot extend any other class. If you c... 2007-03-03, 7268👍, 0💬

What is Collection API
What is Collection API? The Collection API is a set of classes and interfaces that support operation on collections of objects. These classes and interfaces are more flexible, more powerful, and more regular than the vectors, arrays, and hashtables. Example of classes: HashSet, HashMap, ArrayList, L... 2007-03-03, 6378👍, 0💬

Differences between Interfaces and Abstract Classes
What's the difference between an interface and an abstract class? An abstract class may contain code in method bodies, which is not allowed in an interface. With abstract classes, you have to inherit your class from it and Java does not allow multiple inheritance. On the other hand, you can implemen... 2007-03-03, 6175👍, 0💬

Swing BorderLayout and Contrainer Classes
Name the containers which uses Border Layout as their default layout? Swing container classes which uses BorderLayout as their default are: Window, Frame and Dialog classes. 2007-03-03, 6035👍, 0💬

Defining Abstract Classes
How to define an Abstract class? Defining an abstract class is done using the keyword "abstract". Here is an example of abstract class: abstract class MyAbstract { protected String myString; public String getMyString() { return myString; } public abstract string getMyStringInYourWay(); } 2007-03-03, 5944👍, 0💬

Iterator Interface
Is Iterator a Class or Interface? What is its use? Iterator is an interface which is used to step through the elements of a Collection. 2007-03-03, 5931👍, 0💬

All rights in the contents of this web site are reserved by the individual author. fyicenter.com does not guarantee the truthfulness, accuracy, or reliability of any contents.