我想要这样的东西:

public class Stream
{
    public startTime;
    public endTime;

    public getDuration()
    {
        return startTime - endTime;
    }
}

同样重要的是,例如,如果startTime是23:00,endTime是1:00,则持续时间为2:00。

为了在Java中实现这一点,应该使用哪些类型?


当前回答

为了在Java中实现这一点,应该使用哪些类型?

答:长

public class Stream {
    public long startTime;
    public long endTime;

    public long getDuration() {
        return endTime - startTime;
    }
    // I  would add
    public void start() {
        startTime = System.currentTimeMillis();
    }
    public void stop() {
         endTime = System.currentTimeMillis();
     }
}

用法:

  Stream s = .... 

  s.start();

  // do something for a while 

  s.stop();

  s.getDuration(); // gives the elapsed time in milliseconds. 

这是我对你第一个问题的直接回答。

最后一个“注释”,我建议你使用Joda Time。它包含一个适合您需要的间隔类。

其他回答

如果目的只是将粗略的计时信息打印到程序日志中,那么Java项目的简单解决方案不是编写自己的秒表或计时器类,而是使用Apache Commons Lang中的org.apache.commons.lang.time.StopWatch类。

final StopWatch stopwatch = new StopWatch();
stopwatch.start();
LOGGER.debug("Starting long calculations: {}", stopwatch);
...
LOGGER.debug("Time after key part of calcuation: {}", stopwatch);
...
LOGGER.debug("Finished calculating {}", stopwatch);

用这个:

SimpleDateFormat format = new SimpleDateFormat("HH:mm");

Date d1 = format.parse(strStartTime);
Date d2 = format.parse(strEndTime);

long diff = d2.getTime() - d1.getTime();
long diffSeconds,diffMinutes,diffHours;

if (diff > 0) {
diffSeconds = diff / 1000 % 60;
diffMinutes = diff / (60 * 1000) % 60;
diffHours = diff / (60 * 60 * 1000);
}
else{
long diffpos = (24*((60 * 60 * 1000))) + diff;
diffSeconds = diffpos / 1000 % 60;
diffMinutes = diffpos / (60 * 1000) % 60;
diffHours = (diffpos / (60 * 60 * 1000));
}

(同样重要的是,例如,如果startTime是23:00,endTime是1:00,则持续时间为2:00。)

“else”部分可以得到正确的答案

不幸的是,目前发布的十个答案中没有一个是完全正确的。

如果您正在测量经过的时间,并且希望它是正确的,那么必须使用System.nanoTime()。您不能使用System.currentTimeMillis(),除非您不介意结果是错误的。

The purpose of nanoTime is to measure elapsed time, and the purpose of currentTimeMillis is to measure wall-clock time. You can't use the one for the other purpose. The reason is that no computer's clock is perfect; it always drifts and occasionally needs to be corrected. This correction might either happen manually, or in the case of most machines, there's a process that runs and continually issues small corrections to the system clock ("wall clock"). These tend to happen often. Another such correction happens whenever there is a leap second.

由于nanoTime的目的是测量经过的时间,因此它不受任何这些小修正的影响。它是你想要使用的。当前使用currentTimeMillis进行的任何计时都将关闭——甚至可能为负值。

您可能会说,“这听起来似乎并没有那么重要”,对此我说,也许不是,但总的来说,正确的代码不就是比错误的代码好吗?此外,nanoTime打字时间更短。

之前发布的关于nanoTime通常只有微秒精度的免责声明是有效的。此外,它可能需要超过一微秒的时间来调用,这取决于环境(另一个也是如此),所以不要期望对非常非常小的间隔进行正确的计时。

你的新类:

public class TimeWatch {    
    long starts;

    public static TimeWatch start() {
        return new TimeWatch();
    }

    private TimeWatch() {
        reset();
    }

    public TimeWatch reset() {
        starts = System.currentTimeMillis();
        return this;
    }

    public long time() {
        long ends = System.currentTimeMillis();
        return ends - starts;
    }

    public long time(TimeUnit unit) {
        return unit.convert(time(), TimeUnit.MILLISECONDS);
    }
}

用法:

    TimeWatch watch = TimeWatch.start();
    // do something
    long passedTimeInMs = watch.time();
    long passedTimeInSeconds = watch.time(TimeUnit.SECONDS);

之后,所经过的时间可以转换为任何你喜欢的格式,例如日历

Greetz, 查德

如果你喜欢使用Java的日历API,你可以试试这个,

Date startingTime = Calendar.getInstance().getTime();
//later on
Date now = Calendar.getInstance().getTime();
long timeElapsed = now.getTime() - startingTime.getTime();