java - 抽象类是否/可以取代接口(interface)？

Question

这个问题在这里已经有了答案:

When to use an interface instead of an abstract class and vice versa? (26 个回答)

关闭 5年前.

在 Java 中，您可以创建一个只包含抽象方法的抽象类。另一方面，您可以创建一个声明相同方法的接口(interface)。既然如此，可以用抽象类代替接口(interface)吗？

Answer 1

并非总是如此:

• 一个类只能扩展一个类
• 一个类可以实现多个接口(interface)

Sun docs进行更详细的比较:

Abstract Classes versus Interfaces

Unlike interfaces, abstract classes can contain fields that are not static and final, and they can contain implemented methods. Such abstract classes are similar to interfaces, except that they provide a partial implementation, leaving it to subclasses to complete the implementation. If an abstract class contains only abstract method declarations, it should be declared as an interface instead.

Multiple interfaces can be implemented by classes anywhere in the class hierarchy, whether or not they are related to one another in any way. Think of Comparable or Cloneable, for example.

By comparison, abstract classes are most commonly subclassed to share pieces of implementation. A single abstract class is subclassed by similar classes that have a lot in common (the implemented parts of the abstract class), but also have some differences (the abstract methods).