java中抽象类继承抽象类_Java中的抽象类用示例解释

java中抽象类继承抽象类

Abstract classes are classes declared with abstract. They can be subclassed or extended, but cannot be instantiated. You can think of them as a class version of interfaces, or as an interface with actual code attached to the methods.

抽象类是用abstract声明的类。它们可以被子类化或扩展，但是不能被实例化。您可以将它们视为接口的类版本 ，或与方法附带实际代码的接口。

For example, say you have a class Vehicle which defines the basic functionality (methods) and components (object variables) that vehicles have in common.

例如，假设您有一个Vehicle类，它定义了Vehicle共有的基本功能(方法)和组件(对象变量)。

You cannot create an object of Vehicle because a vehicle is itself an abstract, general concept. Vehicles have wheels and motors, but the number of wheels and the size of motors can differ greatly.

您无法创建Vehicle对象，因为Vehicle本身就是一个抽象的通用概念。车辆具有车轮和电动机，但是车轮的数量和电动机的尺寸可能相差很大。

You can, however, extend the functionality of the vehicle class to create a Car or a Motorcycle:

但是，您可以扩展Vehicle类的功能来创建Car或Motorcycle ：

abstract class Vehicle
{//variable that is used to declare the no. of wheels in a vehicleprivate int wheels;//Variable to define the type of motor usedprivate Motor motor;//an abstract method that only declares, but does not define the start //functionality because each vehicle uses a different starting mechanismabstract void start();
}public class Car extends Vehicle
{...
}public class Motorcycle extends Vehicle
{...
}

Remember, you cannot instantiate a Vehicle anywhere in your program – instead, you can use the Car and Motorcycle classes you declared earlier and create instances of those:

请记住，您不能在程序中的任何地方实例化Vehicle ，而是可以使用之前声明的Car和Motorcycle类并创建这些实例：

Vehicle newVehicle = new Vehicle();    // Invalid
Vehicle car = new Car();  // valid
Vehicle mBike = new Motorcycle();  // validCar carObj = new Car();  // valid
Motorcycle mBikeObj = new Motorcycle();  // valid