首先，System.currentTimeMillis()和Instant.now()对于计时来说并不理想。它们都报告了挂钟时间，而计算机并不能准确地知道这个时间，而且它可能会不规律地移动，例如，如果NTP守护进程更正了系统时间，就会往回走。如果计时发生在一台机器上，那么应该使用System.nanoTime()。

其次，从Java 8开始，Java .time. duration是表示持续时间的最佳方式:

long start = System.nanoTime();
// do things...
long end = System.nanoTime();
Duration duration = Duration.ofNanos(end - start);
System.out.println(duration); // Prints "PT18M19.511627776S"
System.out.printf("%d Hours %d Minutes %d Seconds%n",
        duration.toHours(), duration.toMinutes() % 60, duration.getSeconds() % 60);
// prints "0 Hours 18 Minutes 19 Seconds"

手工划分，或者使用SimpleDateFormat API。

long start = System.currentTimeMillis();
// do your work...
long elapsed = System.currentTimeMillis() - start;
DateFormat df = new SimpleDateFormat("HH 'hours', mm 'mins,' ss 'seconds'");
df.setTimeZone(TimeZone.getTimeZone("GMT+0"));
System.out.println(df.format(new Date(elapsed)));

Edit by Bombe:评论中显示，这种方法只适用于较短的持续时间(即少于一天)。

使用java.util.concurrent.TimeUnit类:

String.format("%d min, %d sec", 
    TimeUnit.MILLISECONDS.toMinutes(millis),
    TimeUnit.MILLISECONDS.toSeconds(millis) - 
    TimeUnit.MINUTES.toSeconds(TimeUnit.MILLISECONDS.toMinutes(millis))
);

注意:TimeUnit是Java 1.5规范的一部分，但是toMinutes是在Java 1.6中添加的。

为0-9的值添加前导零，只需执行以下操作:

String.format("%02d min, %02d sec", 
    TimeUnit.MILLISECONDS.toMinutes(millis),
    TimeUnit.MILLISECONDS.toSeconds(millis) - 
    TimeUnit.MINUTES.toSeconds(TimeUnit.MILLISECONDS.toMinutes(millis))
);

如果TimeUnit或toMinutes不受支持(例如在API版本9之前的Android上)，使用以下公式:

int seconds = (int) (milliseconds / 1000) % 60 ;
int minutes = (int) ((milliseconds / (1000*60)) % 60);
int hours   = (int) ((milliseconds / (1000*60*60)) % 24);
//etc...

这个答案与上面的一些答案相似。然而，我觉得这将是有益的，因为与其他答案不同，这将删除任何额外的逗号或空格，并处理缩写。

/**
 * Converts milliseconds to "x days, x hours, x mins, x secs"
 * 
 * @param millis
 *            The milliseconds
 * @param longFormat
 *            {@code true} to use "seconds" and "minutes" instead of "secs" and "mins"
 * @return A string representing how long in days/hours/minutes/seconds millis is.
 */
public static String millisToString(long millis, boolean longFormat) {
    if (millis < 1000) {
        return String.format("0 %s", longFormat ? "seconds" : "secs");
    }
    String[] units = {
            "day", "hour", longFormat ? "minute" : "min", longFormat ? "second" : "sec"
    };
    long[] times = new long[4];
    times[0] = TimeUnit.DAYS.convert(millis, TimeUnit.MILLISECONDS);
    millis -= TimeUnit.MILLISECONDS.convert(times[0], TimeUnit.DAYS);
    times[1] = TimeUnit.HOURS.convert(millis, TimeUnit.MILLISECONDS);
    millis -= TimeUnit.MILLISECONDS.convert(times[1], TimeUnit.HOURS);
    times[2] = TimeUnit.MINUTES.convert(millis, TimeUnit.MILLISECONDS);
    millis -= TimeUnit.MILLISECONDS.convert(times[2], TimeUnit.MINUTES);
    times[3] = TimeUnit.SECONDS.convert(millis, TimeUnit.MILLISECONDS);
    StringBuilder s = new StringBuilder();
    for (int i = 0; i < 4; i++) {
        if (times[i] > 0) {
            s.append(String.format("%d %s%s, ", times[i], units[i], times[i] == 1 ? "" : "s"));
        }
    }
    return s.toString().substring(0, s.length() - 2);
}

/**
 * Converts milliseconds to "x days, x hours, x mins, x secs"
 * 
 * @param millis
 *            The milliseconds
 * @return A string representing how long in days/hours/mins/secs millis is.
 */
public static String millisToString(long millis) {
    return millisToString(millis, false);
}

使用java . util . concurrent。TimeUnit，使用这个简单的方法:

private static long timeDiff(Date date, Date date2, TimeUnit unit) {
    long milliDiff=date2.getTime()-date.getTime();
    long unitDiff = unit.convert(milliDiff, TimeUnit.MILLISECONDS);
    return unitDiff; 
}

例如:

SimpleDateFormat sdf = new SimpleDateFormat("yy/MM/dd HH:mm:ss");  
Date firstDate = sdf.parse("06/24/2017 04:30:00");
Date secondDate = sdf.parse("07/24/2017 05:00:15");
Date thirdDate = sdf.parse("06/24/2017 06:00:15");

System.out.println("days difference: "+timeDiff(firstDate,secondDate,TimeUnit.DAYS));
System.out.println("hours difference: "+timeDiff(firstDate,thirdDate,TimeUnit.HOURS));
System.out.println("minutes difference: "+timeDiff(firstDate,thirdDate,TimeUnit.MINUTES));
System.out.println("seconds difference: "+timeDiff(firstDate,thirdDate,TimeUnit.SECONDS));

    long startTime = System.currentTimeMillis();
    // do your work...
    long endTime=System.currentTimeMillis();
    long diff=endTime-startTime;       
    long hours=TimeUnit.MILLISECONDS.toHours(diff);
    diff=diff-(hours*60*60*1000);
    long min=TimeUnit.MILLISECONDS.toMinutes(diff);
    diff=diff-(min*60*1000);
    long seconds=TimeUnit.MILLISECONDS.toSeconds(diff);
    //hour, min and seconds variables contains the time elapsed on your work