抛出ClassCastException在BookingApp

Question

我在得到一个ClassCastException：

RVBooking rvbooking = (RVBooking) bookingList.get(iweight); 

我要存储用户的weightvehicle输入和调用recordWeight（）方法。对不起，如果我没有解释清楚。提前致谢。

堆栈跟踪

FerryBookingSystem [Java Application] 
    bookingSystem.FerryBookingSystem at localhost:51019 
     Thread [main] (Suspended (exception ClassCastException))  
      FerryBookingSystem.recordVehicleWeight() line: 144 
      FerryBookingSystem.main(String[]) line: 191 
    C:\Program Files\Java\jre7\bin\javaw.exe (16/05/2013 12:42:10 AM) 

BookingException

class BookingException extends Exception{ 
    String message; 
    String IDs; 

    public BookingException(String message){ 
     this.message = message; 
    } 
    public BookingException(String message, String IDs){ 
     this.message = message; 
     this.IDs = IDs; 
    } 
    public String getIDs(){ 
     return IDs; 
    } 
    public String getMessage(){ 
     return message; 
    } 
} 

FerryBookingSystem类

public class FerryBookingSystem { 
    private static ArrayList<VehicleBooking> bookingList = new ArrayList<VehicleBooking>(); 
    private static ArrayList<RVBooking> rvbookingList = new ArrayList<RVBooking>(); 
    private static Scanner userInput = new Scanner (System.in); 


    public static int bookingIDExists(String IDs){ 
     if (bookingList.size() == -1){ 
      return -1; 
     } 
      for (int i = 0; i < bookingList.size(); i++){ 
      if(bookingList.get(i).getbookingID().equals(IDs)){ 
       return i; 
      } 
      } 
      return -1; 
     } 
    public static int rvbookingIDExists(String IDs){ 
     if (rvbookingList.size() == -1){ 
      return -1; 
     } 
      for(int i = 0; i < rvbookingList.size(); i++){ 
      if(rvbookingList.get(i).getbookingID().equals(IDs)){ 
       return i; 
      } 
      } 
      return -1; 
    } 
public static boolean recordVehicleWeight(){ 
    String booking_ID; 
    double weight = 0; 
    int iweight = 0; 
    System.out.print("Please enter the booking ID: "); 
    booking_ID = userInput.nextLine(); 
    if(bookingIDExists(booking_ID) != -1){ 
     if(rvbookingIDExists(booking_ID) != 1){ 
     RVBooking rvbooking = (RVBooking) bookingList.get(iweight); 
     System.out.print("Please enter the weight of the vehicle: "); 
     weight = userInput.nextDouble(); 
     iweight = (int)weight; 
     rvbooking.recordWeight(iweight); 
     return true; 
     } 
     else{ 
     System.out.println("Error - cannot record weight for vehicle booking!"); 
     return false; 
     } 
    } 
    else{ 
     System.out.println("The booking ID does not exist, Please try again."); 
     return false; 
    } 
} 

public static void main (String [] args) throws IOException{ 
    char user; 
    do{ 
    System.out.println("**** Ferry Ticketing System ****"); 
    System.out.println(" A - Add Vehicle Booking"); 
    System.out.println(" B - Add Recreational Vehicle Booking"); 
    System.out.println(" C - Display Booking Summary"); 
    System.out.println(" D - Update Insurance Status"); 
    System.out.println(" E - Record Recreational Vehicle Weight"); 
    System.out.println(" F - Compile Vehicle Manifest"); 
    System.out.println(" X - Exit"); 
    System.out.print("Enter your selection: "); 
    String choice = userInput.nextLine().toUpperCase(); 
    user = choice.length() > 0 ? choice.charAt(0) : '\n'; 
    if (choice.trim().toString().length()!=0){ 
    switch (user){ 
     case 'A': 
      addVehicleBooking(); 
      break; 
     case 'B': 
      addRecreationalVehicleBooking(); 
      break; 
     case 'C': 
      displayBookingSummary(); 
      break; 
     case 'D': 
      updateInsuranceStatus(); 
      break; 
     case 'E': 
      recordVehicleWeight(); 
      break; 
     case 'F': 
      break; 
     case 'X': 
      break; 
     default: 
      break; 
      } 
    } 
    }while(user!='X'); 
} 

}

Answer 1

您试图投RVBooking类型从VehicleBooking列表

Answer 2

看起来你bookingList是指存储VehicleBooking类型的对象对象，你试图给该对象转换为RVBooking，而从获得列表

private static ArrayList<VehicleBooking> bookingList = new ArrayList<VehicleBooking>(); 

除非RVBooking是超一流的VehicleBooking，VehicleBooking不能转换为RVBooking