Java 更改了 Arraylist 中的元素 - 需要保留先前的元素并修改其余元素

Question

我的程序是一个火车时刻表，显示城市的到达和出发时间。在程序中，“延迟”输入会提示您输入城市名称和分钟数，以便为该城市的到达时间添加延迟(以分钟为单位)。这些信息全部存储在一个ArrayList中

这是我当前输出的链接:Train Schedule

这是我的延迟方法:

public void delay(String station, int minutes) {
    // negative delay in minutes are allowed but no guarantee of the
    // consistency of schedules of previous stations
    boolean startDelay = false;
    ListIterator<Station> sIt = schedule.listIterator();
    while (sIt.hasNext()) {

        // first find out the index of station
        Station currStation = sIt.next();

        if (!startDelay && currStation.getCity().equals(station)) {
            startDelay = true;

        } else {
            currStation.delay(minutes);

        }
    }
    startDelay = false;
}

<小时/>

但是，正是在这一点上，我必须将这些相同的分钟添加到列表中的其余时间，但不能在实现延迟之前将这些更改应用于城市。

例如，如果我输入“Edmonton”和“30”，输出应如下所示:

Link to what output should look like

<小时/>

这是我的主要方法:

     public static void main(String[] args) throws ParseException {
        ArrayList<Station> schedule = new ArrayList<Station>();
        SimpleDateFormat sdf = new SimpleDateFormat("d HH:mm");
        schedule.add(new Station(null, sdf.parse("1 20:30"), "Vancouver"));
        schedule.add(new Station(sdf.parse("2 06:00"), sdf.parse("2 06:35"), "Kamloops"));
        schedule.add(new Station(sdf.parse("2 16:00"), sdf.parse("2 17:30"), "Jasper"));
        schedule.add(new Station(sdf.parse("2 23:00"), sdf.parse("2 23:59"), "Edmonton"));
        schedule.add(new Station(sdf.parse("3 08:00"), sdf.parse("3 08:25"), "Saskatoon"));
        schedule.add(new Station(sdf.parse("3 20:45"), sdf.parse("3 22:30"), "Winnipeg"));
        schedule.add(new Station(sdf.parse("4 05:02"), sdf.parse("4 05:42"), "Sioux Lookout"));
        schedule.add(new Station(sdf.parse("4 15:35"), sdf.parse("4 16:10"), "Hornepayne"));
        schedule.add(new Station(sdf.parse("5 00:18"), sdf.parse("5 00:48"), "Capreol"));
        schedule.add(new Station(sdf.parse("5 09:30"), null, "Toronto"));

        TrainTimeTable ttt = new TrainTimeTable(schedule);
        Scanner inp = new Scanner(System.in);
        String cmd = "";
        System.out.println(("Timetable for a train travelling between Vancouver and Toronto").toUpperCase());
        while (!cmd.equalsIgnoreCase("Quit")) {

            System.out.print("Input [Quit | Delay | Show] timetable: ");
            cmd = inp.next();
            if (cmd.equalsIgnoreCase("Show")) {
                System.out.println();
                System.out.println("\t\tSHOWING TRAIN SCHEDULE: ");
                ttt.displaySchedule();
            } else if (cmd.equalsIgnoreCase("Delay")) {

                System.out.print("Please enter the station where train is delayed: ");
                String station = inp.next();

                System.out.print("Please enter the delay time in minutes: ");
                int minutes = inp.nextInt();
                ttt.delay(station, minutes);
                System.out.println();
                System.out.println("\t\tSHOWING NEW SCHEDULE: ");
                ttt.displaySchedule();

            }
            System.out.println();
        }
        inp.close();
    }

}

Answer 1

稍作修改即可解决您的问题。当电台名称匹配时，将 startDelay 设置为 true 并添加该电台和所有后续电台的延迟。

public void delay(String station, int minutes) {
  boolean startDelay = false;
  ListIterator<Station> sIt = schedule.listIterator();
  while (sIt.hasNext()) {
    Station currStation = sIt.next();
    if (!startDelay && currStation.getCity().equals(station)) {
      startDelay = true;
    }
    if( startDelay ){
      currStation.delay(minutes);
    }
  }
}

按照 David 的建议进行编辑:简化方法主体，

boolean startDelay = false;
for( Station currStation: schedule ){
  if ...
  if ...
}