Java Gregorian日历计时器

Question

我有这个Java程序，该程序计算了该人响应确认对话框的时间。但是似乎Time1和Time 2都具有相同的值。我在这里做错了什么：

import javax.swing.JOptionPane;
    import java.util.*;

    public class DialogTimer{
        public static void main(String args[]){
            int time1, time2, milli1, milli2, sec1, sec2, timeDifference;
            final int MILLISECSINSECOND =1000;

            JOptionPane.showConfirmDialog(null, "Is stealing ever justified? ");

            GregorianCalendar before=new GregorianCalendar();
                GregorianCalendar after= new GregorianCalendar();


            milli1=before.get(GregorianCalendar.MILLISECOND);
            milli2=after.get(GregorianCalendar.MILLISECOND);


            sec1=before.get(GregorianCalendar.SECOND);
            sec2=after.get(GregorianCalendar.SECOND);

            time1=MILLISECSINSECOND * sec1 + milli1;
            time2=MILLISECSINSECOND * sec2 + milli2;


            //timeDifference=time1 - time2;
            System.out.println(time1);
            System.out.println(time2);


            //JOptionPane.showMessageDialog(null, "It took " + (time1 - time2) + " milliseconds for you to answer");


        }

    }

Answer 1

import javax.swing.JOptionPane;
import java.util.*;

public class DialogTimer{
    public static void main(String args[]){
        int time1, time2, milli1, milli2, sec1, sec2, timeDifference;
        final int MILLISECSINSECOND =1000;

        GregorianCalendar before=new GregorianCalendar();
        milli1=before.get(GregorianCalendar.MILLISECOND);

        JOptionPane.showConfirmDialog(null, "Is stealing ever justified? ");

        GregorianCalendar after= new GregorianCalendar();
        milli2=after.get(GregorianCalendar.MILLISECOND);


        sec1=before.get(GregorianCalendar.SECOND);
        sec2=after.get(GregorianCalendar.SECOND);

        time1=MILLISECSINSECOND * sec1 + milli1;
        time2=MILLISECSINSECOND * sec2 + milli2;


        //timeDifference=time1 - time2;
        System.out.println(time1);
        System.out.println(time2);


        //JOptionPane.showMessageDialog(null, "It took " + (time1 - time2) + " milliseconds for you to answer");


    }

}

Answer 2

为什么不直接使用System.CurrentTimeMillis（）？例如：

long startAt = System.currentTimeMillis();
... your code ...
long elapsed = System.currentTimeMillis() - startAt;

Answer 3

CodegistCrest是正确的。但是无论如何，您将获得相同或几乎相同的值。现代计算机非常快，但是您从日历获得的时间分辨率和CurrentTimeMillis（）是毫秒。计算机在不到1毫秒的时间内调用您的程序。

在现实生活中，您不需要这一切。你不得不说：

long before = System.currentTimeMillis();

当您显示对话框时

long after = System.currentTimeMillis();

作为用户按下按钮时称为操作的一部分。然后说

time = after - before;