Parse to LocalTime pattern mm:ss.S

DateTimeFormatterBuilder#parseDefaulting

You can use DateTimeFormatterBuilder#parseDefaulting to default the hour of the day to zero.

However, in common sense, 10:38.0 represents a duration. You can obtain a Duration object by finding the duration between the parsed LocalTime and LocalTime.MIN.

Demo:

import java.time.Duration; import java.time.LocalTime; import java.time.format.DateTimeFormatter; import java.time.format.DateTimeFormatterBuilder; import java.time.temporal.ChronoField; import java.util.Locale; public class Main { public static void main(String[] args) { String str = "10:38.0"; DateTimeFormatter dtf = new DateTimeFormatterBuilder() .parseDefaulting(ChronoField.HOUR_OF_DAY, 0) .appendPattern("mm:ss.S") .toFormatter(Locale.ENGLISH); LocalTime time = LocalTime.parse(str, dtf); System.out.println(time); Duration duration = Duration.between(LocalTime.MIN, time); System.out.println(duration); } } 

Output:

00:10:38 PT10M38S 

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The problem is, mm:ss isn't really a local time. It's more like a sprint race time. The error occurs because the translation demands a value for # of hours passed, and none are available ('no hours' is interpreted here as: They weren't in the pattern, not: "They were missing, therefore lets assume there are 0 hours").

One hacky way to fix that is to change your pattern to [HH:]mm:ss - the [] indicates optional input. Now the meaning changes: just 10:20 is interpreted as (via the optional input aspect) a shorthand for 00:10:20 and that is parsable into a LocalTime.

But, perhaps LocalTime isn't quite what you're looking for here; if indeed this describes the time passed to measure an event, you're looking for Duration, not LocalTime. Unfortunately, parsing 10:20 into a duration of 10 minutes and 20 seconds is non-trivial, the API just doesn't support it (only way to get there from a DTFormatter object is via LocalTime, crazily enough).

a) Parsing an expression like mm:ss.S without hours is not possible with the class DateTimeFormatter because such a parser tries to interprete it as point in time, not as duration. The missing hour is a fixed requirement for resolving the result to an instance of LocalTime.

b) You probably want a duration, not a LocalTime. Well, java.time has indeed a class named java.time.Duration but it can only format and parse a subset of ISO-8601-like expressions, for example: PT10M38.2S The pattern you want is not supported. Sorry.

c) Some people suggest a compromise by saying: Interprete LocalTime as kind of duration (not really true!) then parse the expression with a default hour value and finally evaluate the minute-of-hour and second-of-minute and so on. However, such a hacky workaround will only work if you never get time component values greater than 59 minutes or 59 seconds.

d) My external library Time4J supports pattern-based printing and parsing of durations. Example using the class net.time4j.Duration.Formatter:

@Test public void example() throws ParseException { TemporalAmount ta = Duration.formatter(ClockUnit.class, "mm:ss.f") .parse("10:38.2") .toTemporalAmount(); System.out.println(LocalTime.of(5, 0).plus(ta)); // 05:10:38.200 } 

The example also demonstrates a bridge to Java-8-classes like LocalTime via the conversion method toTemporalAmount(). If you use net.time4j.PlainTime instead then the bridge is of course not necessary.

Furthermore, one of many features of the time4j-duration-class is controlled normalizing when an expression contains a time component which does not fit into a standard clock scheme like 10 minutes and 68 seconds (= 11min + 8 sec).

@Test public void example2() throws ParseException { net.time4j.Duration dur = Duration.formatter(ClockUnit.class, "mm:ss.f") .parse("10:68.2") .with(Duration.STD_CLOCK_PERIOD); // normalizing System.out.println(PlainTime.of(5, 0).plus(dur)); // 05:11:08.200 } 

I believe you want: .ofPattern("H:mm.s")

 public static LocalTime parseTime(String time) { return LocalTime.parse(time, DateTimeFormatter.ofPattern("H:mm.s")); } 

https://docs.oracle.com/javase/8/docs/api/java/time/format/DateTimeFormatter.html