Question

我正在创建一个时间应用程序，用于计算当前时间和自1970年1月1日午夜以来经过的时间（以毫秒为单位）。我继续使用Calendar并且能够成功返回当前时间，但由于某种原因，经过的时间返回0.不确定为什么会这样。

这是我目前的代码：

import java.util.Calendar;
import java.util.TimeZone;

public class TimeApp {
  public static void main(String[] args) {
     Time time1 = new Time();
     System.out.println("Hour: " + time1.getHour() + " Minute: " +
                   time1.getMinute() + " Second: " + time1.getSecond());

     Time time2 = new Time();
     System.out.println("Elapsed time since epoch: " + time2.getElapsedTime());
  }
}

final class Time {
  private int hour;
  private int minute;
  private int second;
  private long secondsSinceEpoch;

  public Time() {
    Calendar calendar = Calendar.getInstance();
    this.second = calendar.get(Calendar.SECOND);
    this.minute = calendar.get(Calendar.MINUTE);
    this.hour = calendar.get(Calendar.HOUR_OF_DAY);
  }

  public Time(long elapsedTime) {
    Calendar calendar = Calendar.getInstance(TimeZone.getTimeZone("UTC"));
    calendar.clear();
    calendar.set(2016, Calendar.SEPTEMBER, 9);
    secondsSinceEpoch = calendar.getTimeInMillis() / 1000L;
  }

@Override
   public String toString() {
     return hour + ":" + minute + ":" + second;
  }

  public int getHour() {
     return hour;
  }

  public int getMinute() {
     return minute;
  }

  public int getSecond() {
     return second;    
  }

  public long getElapsedTime() {
   return secondsSinceEpoch;
  }
}

Answer 1

You aren't setting elapsedTime for time2. I think you wanted

Time time2 = new Time(System.currentTimeMillis());

And as pointed out in the comments, you aren't using elapsedTime in your constructor. Something like

public Time(long elapsedTime) {
    secondsSinceEpoch = elapsedTime / 1000;
}

Answer 2

我认为您使用了time2的错误构造函数，因为您调用了Time()并且此版本未设置secondsSinceEpoch。尝试使用具有任何长值的其他构造函数Time(long elapsedTime)，看看它是否有效。像这样......

Time time2 = new Time(10000);

然后重新编写此构造函数，因为您从不使用elapsedTime，或者完全删除它并重新编写第一个构造函数以将值赋给secondsSinceEpoch。

public Time() {
    Calendar calendar = Calendar.getInstance();
    this.second = calendar.get(Calendar.SECOND);
    this.minute = calendar.get(Calendar.MINUTE);
    this.hour = calendar.get(Calendar.HOUR_OF_DAY);
    secondsSinceEpoch = calendar.getTimeInMillis() / 1000L;
  }

显示自纪元以来经过的时间

2 个答案: