java - Instanceof和Casting，多态

基于我的Link的一个较早的问题，我正在研究有关Casting和Instanceof的更多信息。这是基于HeadFirst书中描述的场景

因此，基本上，我现在有了一个新类（Hybrid），该类从我的Vehicle类继承，我想要做的是将Hybrid对象转换为混合对象，以显示混合对象带来的额外信息。它符合要求，但实际上并没有让我知道导致错误的原因，只是它仅在我标记的行结束。

public class ShowroomDriver {
    public static void main(String[] args) {
    Showroom cars = new Showroom("Cars");
    Hybrid hybrid1 = new Hybrid("Toyota Prius", "Focus", "John Smith", "TOTAP453453987346283",
            getCalendar(2,3,1998), getCalendar(24,2,2012),
            "Right Hand",//Hybrid Only Info Edit: Forgot to commentout
            true,
            'C',
            650, 82.0); //Cost & (Hybrid MPG)

    cars.addVechicle(hybrid1);
    cars.getVechicles();

混合类

import java.util.Calendar;

public class Hybrid extends Vehicle{
    private double consumption;
    private String drive;

    public Hybrid(String Manufacture, String Model, String CustomerName, String Vin,
            Calendar DateManufactured, Calendar Datesold, String Drive,
            boolean HasbeenSold,
            char TaxBand,
            double Cost, double Consumption){

        super(Manufacture, Model, CustomerName, Vin, DateManufactured, Datesold,
                HasbeenSold,
                TaxBand,
                Cost);
        this.consumption = Consumption;
        this.drive = Drive;
    }

    public Double getConsumption() { return this.consumption; }
    public String getDrive() { return this.drive; }
}

新车方法

public void displayDetails(){
    for(int i = 0; i <cars.theVehicles.size(); i++){
        if(this.cars.theVehicles.get(i) instanceof Hybrid){//Error here
            Hybrid thehybrids = (Hybrid)this.cars.theVehicles.get(i);
            System.out.println("Consumption: " + thehybrids.getConsumption()+ "\n" +
                    "Drive: " + thehybrids.getDrive());
        }
    }
}

最佳答案

你需要演员吗？您已经覆盖了displayDetails（）方法来显示特定于混合的信息。因此，您应该只能调用此方法，运行时将确定正确的调用方法。