How to format a duration in java? (e.g format H:MM:SS)

java

prompt-engineering

functions

datetime

byAlex Kataev·Nov 27, 2024

Duration duration = Duration.ofSeconds(3661);
String formatted = String.format("%d:%02d:%02d",
    duration.toHoursPart(), 
    duration.toMinutesPart(), 
    duration.toSecondsPart());
System.out.println(formatted); // 1:01:01, like a secret agent, but with a time travel twist

Duration.toHoursPart(), toMinutesPart(), toSecondsPart(): get the duration's hours, minutes, seconds like a time mining operation.
String.format(): Injects our findings into an H:MM:SS pattern, like time's enigma machine.
Output: Our time code unraveled in H:MM:SS format. Neat, right?

In-depth duration formatting

💡 Here's the breakdown of String.format(): it uses placeholders following a special syntax. For instance, %d represents a decimal integer while %02d ensures the integer always takes up 2 spaces, adding a zero if needed.

Pre-Java 8: Simple Arithmetic Approach

Pre- java.time.Duration era (pre-Java 8), we can still format duration using arithmetic operations.

int sec = 3661;
int hrs = sec / 3600; // Hours: because 3600 seconds make an hour!
int mins = (sec % 3600) / 60; // Minutes: Whatever is left from hours, and one minute has 60 seconds.
int secs = sec % 60; // Seconds: And finally, whatever is left!

String formatted = String.format("%d:%02d:%02d", hrs, mins, secs);
System.out.println(formatted); // 1:01:01, Voila!

⚠️ Don't let integer division fool you, it truncates the decimal part. So, watch for potential pitfalls here!

Java 8 and beyond: Unleashing Duration class

In Java 8+, you have the java.time.Duration at your disposal. It's capable of representing time-based duration with precision and convenience.

Going beyond: Advanced tips and tricks

Negative durations? No problem! Apply Math.abs() before formatting. Your users will thank you.

Duration negDuration = Duration.ofSeconds(-4995);
String formattedNeg = String.format("%d:%02d:%02d",
    Math.abs(negDuration.toHoursPart()),
    Math.abs(negDuration.toMinutesPart()),
    Math.abs(negDuration.toSecondsPart()));
// Ouch, time does not like to go backwards!

If you need more control over duration representation, let's say eliminating zero quantities, you can choose to employ a DateTimeFormatter or Joda-Time.

For those Joda-Time enthusiasts

📘 Joda-Time still shines in the face of Java 8+, especially when PeriodFormatter is needed for custom duration formatting.

// Create journey period using Joda-Time
Period period = new Period(totalMillis);
PeriodFormatter formatter = new PeriodFormatterBuilder()
    .printZeroRarelyLast()
    .appendHours()
    .appendSeparator(":")
    .appendMinutes()
    .appendSeparator(":")
    .appendSeconds()
    .toFormatter(); 
// Phew, lots of appending, but hey it works!
String formatted = formatter.print(period);

🔄 Also, if you need a duration between two LocalDateTime instances:

LocalDateTime start = LocalDateTime.now();
LocalDateTime end = LocalDateTime.now().plusHours(3).plusMinutes(25).plusSeconds(42);

Duration between = Duration.between(start, end); // 007 is on a mission. His time to complete it: 3 hours, 25 minutes, and 42 seconds.