What is similarities/difference between an Abstract class and Interface?

Java Interview Questions and Answers (part 1)

(Continued from previous question...)

13. What is similarities/difference between an Abstract class and Interface?

Differences are as follows:
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.
Similarities:

Neither Abstract classes or Interface can be instantiated.

(Continued on next question...)

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