Tag: Abstract class vs interface

Main difference is methods of a Java interface are implicitly abstract and cannot have implementations . A Java abstract class can have instance methods that implements a default behavior. Variables declared in a Java interface is by default final. An abstract class may contain non-final variables.

Main difference is methods of a Java interface are implicitly abstract and cannot have implementations . A Java abstract class can have instance methods that implements a default behavior. Variables declared in a Java interface is by default final. An abstract class may contain non-final variables.

Method Resolution The fourth difference between abstract class and interface in Java is that abstract classes are slightly faster than the interface because the interface involves a search before calling any overridden method in Java .

Abstract classes should be used primarily for objects that are closely related, whereas interfaces are best suited for providing a common functionality to unrelated classes . Interfaces are a good choice when we think that the API will not change for a while.

The short answer: An abstract class allows you to create functionality that subclasses can implement or override. An interface only allows you to define functionality, not implement it . And whereas a class can extend only one abstract class, it can take advantage of multiple interfaces.