java - 程序不返回数组元素

Question

下面是一个程序，我需要将 String time 和 int datum 作为对象存储在数组中，然后将它们打印出来。这就是我目前要做的事情。我相信这是我的 recordEvent 方法的问题。

class RecordEvents4 {
   public static void main(String[] args){
      Recorder4 r1 = new Recorder4(100,100,"Wombat Detection");
      r1.recordEvent("10:53",20);
      r1.recordEvent("10:59",20);
      r1.recordEvent("11:05",20);
      r1.recordEvent("12:59",10);
      r1.recordEvent("13:59",10);
      r1.recordEvent("14:06",10);
      r1.printEvents();
   }
}

class Recorder4 {
   int xPos, yPos;
   String eventType;
   EventInformation[] event = new EventInformation[10];

   int xevent = 0;

   final int EVENT_MAX = 10;

   Recorder4(int xPos, int yPos, String eventType){
      this.xPos = xPos;
      this.yPos = yPos;
      this.eventType = eventType;
   }

   public void recordEvent(String time, int datum){
      /*for(int i = 0; i<event.length; i++){
         event[i] = new EventInformation(time, datum);
      }*/

      event[xevent] = new EventInformation(time, datum);

      xevent++; 
      if(xevent > EVENT_MAX){
         System.out.println("Event log overflow - terminating");
         System.exit(1);
      }
   }

   void printEvents(){       
      System.out.println("Record of " + eventType + " events at [" + xPos + "," + yPos + "]");  
      for(int i = 0; i < xevent; i++){
         System.out.println("Event number " + i + " was recorded at " + event[i] + " with datum = " + event[i]);
      }
   }
}

class EventInformation {
   String eventTime;
   int eventDatum;

   EventInformation(String eventTime, int eventDatum){
      this.eventTime = eventTime;
      this.eventDatum = eventDatum;      
   }
}

这就是它的输出:

Record of Wombat Detection events at [100,100]
Event number 0 was recorded at EventInformation@15db9742 with datum = EventInformation@15db9742
Event number 1 was recorded at EventInformation@6d06d69c with datum = EventInformation@6d06d69c
Event number 2 was recorded at EventInformation@7852e922 with datum = EventInformation@7852e922
Event number 3 was recorded at EventInformation@4e25154f with datum = EventInformation@4e25154f
Event number 4 was recorded at EventInformation@70dea4e with datum = EventInformation@70dea4e
Event number 5 was recorded at EventInformation@5c647e05 with datum = EventInformation@5c647e05

这就是我所期待的:

Record of Wombat Detection events at [100,100] 
Event number 0 was recorded at 10:53 with datum = 20 
Event number 1 was recorded at 10:59 with datum = 20 
Event number 2 was recorded at 11:05 with datum = 20 
Event number 3 was recorded at 12:59 with datum = 10 
Event number 4 was recorded at 13:59 with datum = 10 
Event number 5 was recorded at 14:06 with datum = 10

有人建议我使用 toString() ，但我不确定使用 recordEvent() 的方向是否正确，我打算将方法参数分配给 EventInformation 对象，该对象的引用是存储在事件数组的元素中。

Answer 1

您实际上是在要求 Java 打印出事件数组的一个元素。在此数组的声明中，您为其中的元素指定了 EventInformation 类型。默认情况下，Java 显然不知道如何打印它，因为你自己定义了它!要解决此问题，请更改打印语句:

    System.out.println("Event number " + i + " was recorded at " + event[i].eventTime + " with datum = " + event[i].eventDatum);

现在您要求 Java 打印 eventTime (字符串)和 eventDatum (整数)。这些都是 Java 知道如何打印的东西，因为它们是由 Java 本身定义的。