Java的时差 [英] Time difference in Java

问题描述

为什么以下Java代码的输出是04:18:23而不是03:18:23？

Why the output of the Java code below is 04:18:23 and not 03:18:23?

public static void main(String[] args) {
    SimpleDateFormat sdf = new SimpleDateFormat("HH:mm:ss");
    try {
        Date start = sdf.parse("00:44:16");
        Date end = sdf.parse("04:02:39");
        long duration = end.getTime() - start.getTime();
        Calendar cal = Calendar.getInstance();
        cal.setTimeInMillis(duration);
        System.out.println(sdf.format(cal.getTime()));
    } catch (ParseException e) {
        e.printStackTrace();
    }
}

推荐答案

因为这不是你如何得到一个持续时间。将您的代码更改为：

Because that's not how you get a duration. Change your code to this:

package com.sandbox;

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;

public class Sandbox {

    public static void main(String[] args) {
        SimpleDateFormat sdf = new SimpleDateFormat("HH:mm:ss");
        try {
            Date start = sdf.parse("00:44:16");
            Date end = sdf.parse("04:02:39");
            long duration = end.getTime() - start.getTime();
            Calendar cal = Calendar.getInstance();
            cal.setTimeInMillis(duration);
            System.out.println(new SimpleDateFormat("yyyy MM dd HH:mm:ss").format(cal.getTime()));
        } catch (ParseException e) {
            e.printStackTrace();
        }
    }
}

你会看到它打印out 1969 12 31 19:18:23 。那是日期而不是持续时间。由于您在打印答案时正在跳过日期组件，因此它出现就像打印一段时间一样，但事实并非如此。

You'll see it prints out 1969 12 31 19:18:23. That's a date not a duration. Since you're skipping the date components when you print out your answer, it appears like it's printing out a duration, but it's really not.

坦率地说，我不知道如何在java中这样做。我只是使用JodaTime库。有一个名为持续时间的课程，使这一切变得简单。这是一个SO问题，显示如何使用它以任何方式打印结果："漂亮的印刷品持续时间在java

To be frank, I don't know how to do this in java. I just use the JodaTime library. There's a class called Duration that makes this easy. Here's a SO question that shows how to use it to print out the results any way you want: "pretty print" duration in java

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