Question

我一直在创建一个添加搜索删除预订等程序... 几个小时后，我最终认为我正在取得进展，但是当我删除预订时，我的程序发现正确的预订会返回该预订的正确信息，但会删除不同的预订。

我已将文件附加到zip中，就像我显示它们一样，它们占用了大量的屏幕空间。该计划已在BlueJay中制作： hostelgreamenew.zip 18.4 KB

将数据删除和添加到我的数组列表中的代码

public Hostel(String hostelName)
{
    this.hostelName = "Newcastle Hostel";
    bookings = new ArrayList<Booking>();
}
public String getHostelName()
{
    return hostelName;
}
public String addBooking(String roomID, String roomType, String guest)
{
    if (roomID.equals(""))
        return "Error Please Entre Room ID";

    else if (roomType.equals(""))
        return "Error Please Entre Room Type";

    else if (guest.equals(""))
        return "Error Please Entre Guest Name";

    bookings.add(new Booking(roomID,roomType,guest));
    return "Room " + roomID + " " + roomType + " Has Been Booked For " + guest;
}

这取自我的宿舍课程

public String deleteBooking(String roomID)
{
    int index = 0;
    for ( Booking s : bookings )
    {
        if ( s.getRoomID().equals(roomID))
        {
            //return "Room ID: " + roomID + " Room Type: " + s.getRoomType() + " Guest: " + s.getGuest();
            String deleteMessage = "Room ID: " + roomID + "  Room Type: " + s.getRoomType() + "  Guest: " + s.getGuest();


           int response = JOptionPane.showConfirmDialog(null, deleteMessage, "Confirm Delete",
           JOptionPane.YES_NO_OPTION, JOptionPane.QUESTION_MESSAGE);
           if (response == JOptionPane.NO_OPTION) 
           {
           } else if (response == JOptionPane.YES_OPTION) 
           {
           bookings.remove(index);    
           } 
           index++;

        }

    }
    return  "  Cannot find room";
}

这取自我的GUI类

else if (item.equals("Cancel Booking"))
    {
        newBookingButton.setEnabled(false);
        cancelBookingButton.setEnabled(false);
        String roomID = JOptionPane.showInputDialog(this, "Enter a room ID", "Delete a Booking", JOptionPane.QUESTION_MESSAGE);
        output.setText(hostel.deleteBooking(roomID));
        newBookingButton.setEnabled(true);
        cancelBookingButton.setEnabled(true);
    }

任何附加代码都需要询问或上面的链接中有完整的副本，谢谢

Answer 1

如果当前房间的房间ID等于要删除的房间的ID，则您的循环仅递增索引。这条线

index++;

应该在if区块之外。

编辑：

另一个问题是你在迭代时试图删除元素。只有在使用迭代器迭代集合并使用迭代器的remove方法删除当前元素时，才可以执行此操作。请注意，即使有可能，由于您删除了给定索引处的元素，因此您不应该递增索引，因为您刚刚删除了此索引处的元素。

使用迭代器的示例：

for (Iterator<Booking> it = bookings.iterator(); it.hasNext(); ) {
    Booking b = it.next();
    if (...) {
        it.remove();
    }
}

Answer 2

基本上当s.getRoomID().equals(roomID)为真时，您的if块将被执行，因此无论用户的响应是什么，index都会递增。所以，这样做：

if ( s.getRoomID().equals(roomID))
{
   //your code
}

index++

Answer 3

我只是查看了你的代码，看起来你正试图迭代一个集合并同时修改这些值。使用增强的for循环，这样的事情会产生错误，因此不必使用增强的for循环，而是必须使用普通for循环。所以我修改了你的deleteBookings方法以进行相应的更改。

 public String deleteBooking(String roomID)
 {
    //for ( Booking s : bookings )
    for (int i = 0; i < bookings.size(); i++)
    {
        Booking s = bookings.get(i);
        if ( s.getRoomID().equals(roomID))
        {
            //return "Room ID: " + roomID + " Room Type: " + s.getRoomType() + " Guest: " + s.getGuest();
            String deleteMessage = "Room ID: " + roomID + "  Room Type: " + s.getRoomType() + "  Guest: " + s.getGuest();

            //int r = JOptionPane.showOptionDialog,null("Are you sure you would like to delete the following \n"
            //+ "deleteMessage",
            //"Delete a booking",
            //JOptionPane.YES_NO_OPTION,
            //JOptionPane.QUESTION_MESSAGE,null,null,null);

            //if (r == JOptionPane.YES_OPTION) {
            //    bookings.remove(index);
            //}
            //if (r == JOptionPane.NO_OPTION){
           //     return "Booking Was Not Canceled";
           // }
           int response = JOptionPane.showConfirmDialog(null, deleteMessage, "Confirm Delete",
           JOptionPane.YES_NO_OPTION, JOptionPane.QUESTION_MESSAGE);
           if (response == JOptionPane.NO_OPTION) 
           {
           } else if (response == JOptionPane.YES_OPTION) 
           {
           //bookings.remove(index);    
           bookings.remove(i);    
           return deleteMessage + " has been DELETED."; /*I did this.*/
           }                               
        }

    }
    return  "  Cannot find room";
}

此外，在此之后

bookings.remove(i);

你忘了回复

之类的东西

return deleteMessage + " has been DELETED."; /*I did this.*/

由于您在成功完成时未能返回String，因此即使成功删除后，它也会返回“无法找到空间”。其余的代码是完美的。希望这可以解决您的疑问。

此致

从Array List中删除数据字符串

3 个答案: