java - Java中如何对时间求和？

Question

我正在编写一个报告，该报告计算其中的数据总和，其中一些数据是时间戳，例如:

 ----------------------|  Activity |   Time   | ----------------------|     1     | 11:00:00 | -----------------------|     2     | 12:00:00 | -----------------------|     3     | 13:00:00 | -----------------------| Total     | 36:00:00 | ----------------------

I'm trying to sum timestamps as below:

final DateFormat dt = new SimpleDateFormat("HH:mm:ss");
final Calendar c = Calendar.getInstance(TimeZone.getDefault(), Locale.getDefault());
c.setTimeInMillis(0);
for (final String t : timestampsList) {
    c.add(Calendar.MILLISECOND, (int) dt.parse(t).getTime());
}

变量timestampsList是一个ArrayList String 的，全部遵循 SimpleDateFormat 使用的模式目的。给定代码的问题是，我无法通过使用相同的 SimpleDateFormat 生成时间戳总和的值，我得到的是 future 日期通知的模式中的一个小时。

我也看过Joda Time Duration类，但我不熟悉这个库，而且我不知道我是否走在正确的道路上，可以引导我找到正确的答案。

有谁知道如何使用J2SE或Joda Time来处理它？

Answer 1

我会自己解析这些字符串，将它们转换为
秒或毫秒并将它们相加。请参阅下面的答案 2。

答案1

import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.Date;


public class Test051 {

    public static void main(String[] args) throws Exception {
        String pt = "1970-01-01-";
        ArrayList<String> timestampsList = new ArrayList<String>();
        timestampsList.add("01:00:05");
        timestampsList.add("01:00:05");
        timestampsList.add("10:00:05");
        final DateFormat dt = new SimpleDateFormat("yyyy-MM-dd-HH:mm:ss");
        final Calendar sum = Calendar.getInstance();
        sum.setTimeInMillis(0);

        long tm0 = new SimpleDateFormat("yyyy-MM-dd").parse(pt).getTime();

        System.out.println("tm0 = " + tm0);

        for (final String t : timestampsList) {
            // System.out.println(dt.parse(pt + t).getTime());
            Date x = dt.parse(pt + t);
            // System.out.println(x.getTime());
            sum.add(Calendar.MILLISECOND, (int)x.getTime());
            sum.add(Calendar.MILLISECOND, (int)-tm0);
        }

        long tm = sum.getTime().getTime();
        System.out.println("tm = " + tm);

        tm = tm / 1000;


        long hh = tm / 3600;
        tm %= 3600;
        long mm = tm / 60;
        tm %= 60;
        long ss = tm;
        System.out.println(format(hh) + ":" + format(mm) + ":" + format(ss));
    }

    private static String format(long s){
        if (s < 10) return "0" + s;
        else return "" + s;
    }
}

答案2

import java.util.ArrayList;

public class Test051 {

    public static void main(String[] args) throws Exception {
        ArrayList<String> timestampsList = new ArrayList<String>();
        timestampsList.add("01:00:05");
        timestampsList.add("01:00:05");
        timestampsList.add("10:00:05");

        long tm = 0;
        for (String tmp : timestampsList){
            String[] arr = tmp.split(":");
            tm += Integer.parseInt(arr[2]);
            tm += 60 * Integer.parseInt(arr[1]);
            tm += 3600 * Integer.parseInt(arr[0]);
        }

        long hh = tm / 3600;
        tm %= 3600;
        long mm = tm / 60;
        tm %= 60;
        long ss = tm;
        System.out.println(format(hh) + ":" + format(mm) + ":" + format(ss));
    }

    private static String format(long s){
        if (s < 10) return "0" + s;
        else return "" + s;
    }
}

答案3

import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.Date;

public class Test051 {

    public static void main(String[] args) throws Exception {
        ArrayList<String> timestampsList = new ArrayList<String>();
        timestampsList.add("01:00:00");
        timestampsList.add("02:00:00");
        timestampsList.add("03:00:00");
        timestampsList.add("04:00:00");
        timestampsList.add("02:00:00");
        timestampsList.add("04:00:00");

        Date dt0 = new SimpleDateFormat("yyyy-MM-dd").parse("1970-01-01");

        // Check very carefully the output of this one.
        System.out.println(dt0.getTime());

        final DateFormat dt = new SimpleDateFormat("HH:mm:ss");
        final Calendar c = Calendar.getInstance();
        c.setTimeInMillis(0);
        for (final String t : timestampsList) {
            c.add(Calendar.MILLISECOND, (int) dt.parse(t).getTime());
            c.add(Calendar.MILLISECOND, (int)-dt0.getTime());
        }

        // We need to add this back. This is basically the time zone offset.
        c.add(Calendar.MILLISECOND, (int)dt0.getTime());

        System.out.println(c.getTime().getTime());
        System.out.println(c.getTimeInMillis());

        System.out.println(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(c.getTime()));
        System.out.println(new SimpleDateFormat("HH:mm:ss").format(c.getTime()));
    }

}