java - 从 Java 中的抽象类创建子类

Question

目前正在学习 Java，我有一个关于从抽象类创建子类的问题。我有这个:

public abstract class Bike
{
  private int cost;

  public Bike(){}

  public abstract void displayCost();
}


public class SportsBike extends Bike
{
  private int topSpeed();

  ???
}

public class CasualBike extends Bike
    {
      private int brakeSpeed();

      ???
    }


 public void main()
{
  SportsBike b1 = new SportsBike(???);
  CasualBike b2 = new CasualBike(???);
}

我如何拥有sportsBike和casualBike的构造函数，以便它们拥有自己的信息？我已经阅读过有关 @super 等的内容，但我不确定如何实现它。如果我有多个类继承一个类，@override 会起作用吗？

Answer 1

这是一个简单的示例，您可以尝试一下以了解构造函数如何工作，以及如何自动调用父类(super class)构造函数，即使您没有显式调用它们:

public class Parent {
    protected int parentVariable;
    public Parent(){
        parentVariable=1;
        System.out.println("parent no-argument constructor");
    }
    public Parent(int value) {
        System.out.println("parent int constructor");
        parentVariable = value;
    }
    public int getParentVariable() {
        return parentVariable;
    }
}

public class Child extends Parent {
    private int childVariable;

    public Child() {
        // Call super() is automatically inserted by compiler
        System.out.println("child no-argument constructor");
        childVariable = 99;
    }
    public Child(int value, int childValue){
        // Explicit call to parent constructor
        super(value);
        System.out.println("child int constructor");
        childVariable = childValue;
    }
    public int getChildVariable() {
        return childVariable;
    }
}   

public class Driver {

    public static void main(String[] args)
    {
        Child c1 = new Child();
        Child c2 = new Child(3,199);

        System.out.println(c1.getParentVariable());
        System.out.println(c2.getParentVariable());

        System.out.println(c1.getChildVariable());
        System.out.println(c2.getChildVariable());
    }

}