Java 连接两个类

我被困在这个练习中，我应该创建一个叫做Car的第二个类，它链接到Vehicle。它应该是这样的：

vehicle类和testprogram一起工作得很好，但是现在我想将类Car连接到vehicle，然后为Car创建一个testclass。这是我的车辆等级：

public class Vehicle {
int speed;

// Constructor
public Vehicle() {
    this.speed = 0;

}

public class Car extends Vehicle {
    String regnr;

    public Car(String regnr) {
        this.regnr = regnr;
    }

    public String getRegNbr() {
        return this.regnr;
    }

}

public void increaseSpeed(int differenceInc) {
    int currentSpeed = this.speed;
    // Kör loopen så länge den nuvarande hastigheten inte är lika med den önskade
    while (this.speed != (currentSpeed + differenceInc)) {
        this.speed += 1;

        System.out.println("The current speed is increasing to: " + this.speed);
    }

}

public void decreaseSpeed(int differenceDec) {
    int currentSpeed = this.speed;

    while (this.speed != (currentSpeed - differenceDec)) {
        this.speed -= 1;
        System.out.println("The current speed is decreasing to: " + this.speed);
    }

}

public void brake() {
    int currentSpeed = this.speed;
    while (this.speed != 0) {
        this.speed /= 2;
        System.out.println("The current speed is decreasing to: " + this.speed);
    }
}

public int getSpeed() {
    return this.speed;
}

public void testVehicle() {

    Scanner myScanner = new Scanner(System.in);
    while (this.speed != 0) {
        System.out.println("You're driving at: " + " " + this.speed + "KM/H" + "\n\nDo you want to:"
                + "\n(1) Slow down to " + "lower speed??" + "\n(2) Maintain current speed?"
                + "\n(3) Hit the brakes?" + "\n(4) Accelerate even more?");

        int choice = myScanner.nextInt();

        if (choice == 1) {
            System.out.print("By how much would you like to decrease your speed? ");
            Scanner in = new Scanner(System.in);
            int dec = in.nextInt();
            this.decreaseSpeed(dec);
        } else if (choice == 2) {
            System.out.println("Maintaining current speed");
        } else if (choice == 3) {
            System.out.println("Breaking!");
            this.brake();
        }

        else if (choice == 4) {
            System.out.print("By how much would you like to increase your speed? (km/h)");
            Scanner in = new Scanner(System.in);
            int inc = in.nextInt();
            this.increaseSpeed(inc);
        }

        else {
            System.err.println("Incorrect value entererd.");
            System.exit(0);
        }
    }

    if (this.getSpeed() == 0)

    {
        System.out.println("Bilen står still");
    }

}

}

如您所见，testVehicle（）类和一个名为VehicleTest的单独测试程序运行我创建的Vehicle类。我已经将Car类添加到程序中，它应该扩展vehicle。我唯一的问题是如何在测试类中实现它

我当前的单独测试程序如下所示：

public class VehicleTest {

/**
 * @param args
 */
public static void main(String[] args) {
    Vehicle bmw = new Vehicle();
    Scanner scan = new Scanner(System.in);
    System.out.println("How fast do you want to drive?");

    int fast = scan.nextInt();
    bmw.increaseSpeed(fast);
    bmw.testVehicle();
}

---

}

你应该把车从车上伸出来。试试这个：

public class Car1 extends Vehicle {
...
}

所以你们可以像汽车一样使用汽车

---

要阅读的一些信息

从车辆类别中派生您的Car1类别

 public class Car1 extends Vehicle{

    String regnr;

    public Car1(String regnr) {
        super();//pass data to parent constructor if needed
        this.regnr = regnr;
    }

    public String getRegNbr() {
        return regnr;
    }

}

现在，您将能够从Vehicle类调用公共方法

Car1 car = new Car1("DHM1234");
car.increaseSpeed(5); // The current speed is increasing to: 5

如果要更改车辆（父）类的任何公共/受保护方法对车辆类的行为，请重写该方法 i、 e

现在，如果您从car对象调用

brake（）

car.brake(); // Hard break will be printed

---

阅读了解更多信息。

您知道Java中的继承吗？如果没有，请检查我是否编辑了我的初始帖子，以便您可以看到我的位置。我剩下的一件事就是创建测试类，但我不知道它应该在哪里？它应该在我在底部发布的测试程序中，还是应该添加到Vehicle类中的testVehicle方法中？您可以同时执行这两个操作。你这样做也很好。好吧，让我们假设我在程序中说：你的注册号是（…），然后按现在的样子打印程序的其余部分。如果我输入Car1 car=新Car1（“DHM1234”）；车辆下方宝马=新车（）；所有我得到的是“汽车无法解析为类型”你在你的汽车类别内做错了，你的汽车类别应该在汽车类别之外。在一个单独的文件中会更好我到底做错了什么？另外，我是否应该键入Car1 car=new Car1（“DHM1234”）并删除车辆bmw=new Vehicle（），因为car类继承了车辆类？

car.brake(); // Hard break will be printed