java - 我如何返回时间；来自 printDetails 中的 ClockDisplay() 对象？

Question

我需要创建一个历史时刻对象，它从 ClockDisplay() 对象返回时间，我想知道如何返回时间；来自 ClockDisplay() 对象？当我编译它时，它没有错误，但是当我创建一个时间值为 11:00 的 ClockDisplay 对象并创建一个 HistoricalMoment 对象并检查它时，当我 printDetails 时它返回一个空值。

这是我的代码:

/**
 * @return the time
 */
public ClockDisplay getTime()
{
    return time;
}

这是我的打印详细信息:

/**
 * the print details of time and event
*/
public void printDetails()
{
System.out.println("At " + getTime() + "," + getEventName());
}

这是我的 HistoricalMoment 类(class):

public class HistoricalMoment{

private String eventName;
private ClockDisplay timeOfEvent;
private ClockDisplay time;

public static final int MIDNIGHT_HOUR = 00;
public static final int MINUTE_ZERO = 00;

public static final int ELVENTH_HOUR = 11;
public static final int TWO_MINUTES = 02;
public static final int FORTY_MINUTES = 40;
public static final int NINTH_HOUR = 9;
public static final int FOUR_MINUTES = 04;

/**
 * Default Constructor
 */
public HistoricalMoment(){
    eventName = "untitled event";
    timeOfEvent = new ClockDisplay(MIDNIGHT_HOUR, MINUTE_ZERO);

}

/**
 * @param nameOfTheEvent the name of the event; "untitled event" if the name of the event is null or ""
 */
public HistoricalMoment(String nameOfTheEvent){
    if ((nameOfTheEvent == null) || (nameOfTheEvent.equals(""))){
        eventName = "untitled event";
        timeOfEvent = new ClockDisplay(MIDNIGHT_HOUR, MINUTE_ZERO);
    }
    else {
        eventName = nameOfTheEvent;
        timeOfEvent = new ClockDisplay(MIDNIGHT_HOUR, MINUTE_ZERO);
    }

}

/**
 * @param the name and time of the event
 */
public HistoricalMoment(String nameOfTheEvent, ClockDisplay theTime)
{
    if ( (nameOfTheEvent == null) || (nameOfTheEvent.equals(""))){
        eventName = "untitled event";
        timeOfEvent = new ClockDisplay(MIDNIGHT_HOUR, MINUTE_ZERO);
    }
    else{
        eventName = nameOfTheEvent;
        timeOfEvent = theTime;
    }
}

/**
 * @return the time of event
 */
public ClockDisplay getTime()
{
    return timeOfEvent;
}


/**
 * @return the eventName;
 */
public String getEventName()
{
    return eventName;
}

/**
 * @return the time of the event incremented
 */
public void addMinuteToTimeOfEvent(){
    timeOfEvent.timeTick();
}

/**
 * the print details of time and event
 */
public void printDetails()
{
    System.out.println("At " + getTime() + "," + getEventName());
}

}

这是我的 ClockDisplay 类:

public class ClockDisplay
{
private NumberDisplay hours;
private NumberDisplay minutes;
private String displayString;    // simulates the actual display

public static final int FIRST_MORNING_HOUR  = 0;
public static final int LAST_MORNING_HOUR   = 11;
public static final int FIRST_EVENING_HOUR      = 12;
public static final int LAST_EVENING_HOUR       = 23;
public static final int MINUTES_PER_HOUR        = 60;
public static final int MINUTES_ZERO            = 0;
public static final String MORNING_SUFFIX       = "a.m.";
public static final String EVENING_SUFFIX       = "p.m.";
public static final int MIDNIGHT_HOUR       = 0;
public static final int HOURS_PER_DAY       = 0;
public static final int TWENTY_FOUR_HOURS   = 24;
/**
 * Constructor for ClockDisplay objects. This constructor 
 * creates a new clock set at 00:00.
 */
public ClockDisplay()
{
    hours = new NumberDisplay(TWENTY_FOUR_HOURS);
    minutes = new NumberDisplay(MINUTES_PER_HOUR);
    updateDisplay();
}

/**
 * Constructor for ClockDisplay objects. This constructor
 * creates a new clock set at the time specified by the 
 * parameters.
 */
public ClockDisplay(int hour, int minute)
{
    hours = new NumberDisplay(TWENTY_FOUR_HOURS);
    minutes = new NumberDisplay(MINUTES_PER_HOUR);
    setTime(hour, minute);
}

/**
 * This method should get called once every minute - it makes
 * the clock display go one minute forward.
 */
public void timeTick()
{
    minutes.increment();
    if(minutes.getValue() == MINUTES_ZERO){  // it just rolled over!
        hours.increment();
    }
    updateDisplay();
}

/**
 * Set the time of the display to the specified hour and
 * minute.
 */
public void setTime(int hour, int minute)
{
    hours.setValue(hour);
    minutes.setValue(minute);
    updateDisplay();       
}

/**
 * @retun the time from displayString
 */
public String getTime()
{
    return displayString;
}

/**
 * the updated display 
 */
private void updateDisplay()
{
    if(hours.getValue() < FIRST_EVENING_HOUR){
        displayString = hours.getDisplayValue() + ":" +
        minutes.getDisplayValue() + " am";
    }

    else if(hours.getValue() > FIRST_EVENING_HOUR && hours.getValue() <LAST_EVENING_HOUR){
        displayString = Integer.toString(hours.getValue() - FIRST_EVENING_HOUR) + ":" + 
        minutes.getDisplayValue() + " pm";
    }
    else if(hours.getValue() == MIDNIGHT_HOUR){
        hours.setValue(FIRST_EVENING_HOUR); 
        displayString = hours.getDisplayValue() + ":"+
        minutes.getDisplayValue() + " am (midnight)";    
    }  
    else{
        hours.setValue(FIRST_EVENING_HOUR);
        displayString = hours.getDisplayValue() + ":" + 
        minutes.getDisplayValue() + " pm (noon)";
    }
}
}

Answer 1

所以经过相当长的时间思考后我发现我必须做的就是调用 timeOfEvent 获取值以与 ClockDisplay 值一致。

这是我遇到问题的 printDetails 的编码。希望它能对其 future 的其他人有所帮助。

public void printDetails()
    {
        System.out.println("At " + timeOfEvent.getTime() + ", " + eventName);
    }

以下是带有更正的 HistoricalMoments 类的完整编码:

public class HistoricalMoment{

private String eventName;
private ClockDisplay timeOfEvent;

public static final int MIDNIGHT_HOUR = 00;
public static final int MINUTE_ZERO = 00;

public static final int ELVENTH_HOUR = 11;
public static final int TWO_MINUTES = 02;
public static final int FORTY_MINUTES = 40;
public static final int NINTH_HOUR = 9;
public static final int FOUR_MINUTES = 04;

/**
 * Default Constructor
 */
public HistoricalMoment(){
    eventName = "untitled event";
    timeOfEvent = new ClockDisplay(MIDNIGHT_HOUR, MINUTE_ZERO);

}

/**
 * @param nameOfTheEvent the name of the event; "untitled event" if the name of the event is null or ""
 */
public HistoricalMoment(String nameOfTheEvent){
    if ((nameOfTheEvent == null) || (nameOfTheEvent.equals(""))){
        eventName = "untitled event";
        timeOfEvent = new ClockDisplay(MIDNIGHT_HOUR, MINUTE_ZERO);
    }
    else {
        eventName = nameOfTheEvent;
        timeOfEvent = new ClockDisplay(MIDNIGHT_HOUR, MINUTE_ZERO);
    }

}

/**
 * @param the name and time of the event
 */
public HistoricalMoment(String nameOfTheEvent, ClockDisplay theTime)
{
    if ( (nameOfTheEvent == null) || (nameOfTheEvent.equals(""))){
        eventName = "untitled event";
        timeOfEvent = new ClockDisplay(MIDNIGHT_HOUR, MINUTE_ZERO);
    }
    else{
        eventName = nameOfTheEvent;
        timeOfEvent = theTime;
    }
}

/**
 * @return the time of the event incremented
 */
public void addMinuteToTimeOfEvent(){
    timeOfEvent.timeTick();
}

/**
 * the print details of time and event
 */
public void printDetails()
{
    System.out.println("At " + timeOfEvent.getTime() + ", " + eventName);
}

}