Java编程之继承问题代码示例

package bzu.aa;public class Vehicle {  protected int capacity;  public Vehicle (){    capacity=2;    System.out.println("执行交通工具类的无参构造方法.");  }  public Vehicle(int capacity){    //super();    this.capacity=capacity;    System.out.println("执行交通工具类的有参构造方法.");  }  public int getCapacity(){    return capacity;  }  public void setCapacity(int capacity){    this.capacity=capacity;   }  public void print(){    System.out.println("交通工具的载客量为:"+capacity);   }}Car类：package bzu.aa;public class Car extends Vehicle {  protected int speed;  public Car(){    super();    speed=0;    System.out.println("执行汽车类的无参构造方法.");    }  public Car(int speed){    super(6);    this.speed=speed;      System.out.println("执行汽车类的有参构造方法.");    }  public int speedUp(int speed){    this.speed=speed+10;    return speed;  }  public int speedDown(int speed){    this.speed=speed-10;    return speed;  }  public void print(){    System.out.println("汽车的载客量为:"+capacity+";汽车的速度为:"+speed);  }  }Bus类：package bzu.bb;import bzu.aa.Car;public final class Bus extends Car{  public int capacity;  public Bus(){    super();    capacity=20;    System.out.println("执行公交车类的无参构造方法.");    }  public Bus(int capacity){    super(40);    this.capacity=capacity;    System.out.println("执行公交车类的有参构造方法.");    }  public void print(){    System.out.println("公交车的的载客量为:"+capacity+";公交车的速度为:"+speed+";汽车类的载客量为:"+getCapacity());  }  }Test类：package bzu.bb;import bzu.aa.Car;public class Test {  public static void main(String[] args) {    Car car=new Car();    car.speedUp(40);    car.print();    car.speedDown(30);    car.print();    Bus bus=new Bus(20);    bus.print();  }}