System.currenttimemillis() vs. new Date() vs. Calendar.getInstance().getTime()
For just-in-time Java:
System.currentTimeMillis()is your most efficient stopwatch delivering current time in milliseconds without any baggage.new Date()is for when you need more than just the time - the full package, albeit a tad slower than the pure millisecond form.Calendar.getInstance().getTime()should be your last resort if you're only out for a timestamp - it brings performance-hungry machinery along.
Let's dive into the swimming pool of details! No worries, life jackets are provided πββοΈ
A closer look at performance π
System.currentTimeMillis() is about as close as you can get to the bare metal in Java for high-precision timing tasks. It's fast and lean, ideal for measuring time intervals or benchmarking code.
For cases where you need a physical object representation of time, new Date() can serve as your trusty time capsule! It's still quite speedy but carries some minor baggage - itself!
Out for some heavy lifting? Calendar.getInstance().getTime() is the bulldozer of Java time management. It creates not one, but two objects (a Calendar and a Date internally) every time. Not designed for frequent-flyer timekeeping tasks, use this beast for in-depth calendar operations.
Is your application human-friendly? π€
System.currentTimeMillis() returns a cryptic long number, which while machine-friendly, doesn't really tell humans much. Need to turn this into a human-readable date? Welcome Date and SimpleDateFormat or DateTimeFormatter to the stage!
Remember, creating these objects isn't free. It's all a balancing act between performance and user experience.
Daylight saving time - friend or foe? β°
System.currentTimeMillis() is oblivious to factors like daylight-saving changes, but both Date and Calendar take account of the local timezone settings. This can produce some interesting results (not always desired ones π€¦ββοΈ) when dealing with global applications or time logs.
Practical tips for the busy developer β‘
- Need accurate timing for your some-kind-of-a-clock app?
System.currentTimeMillis()is your best friend. - Looking to work with time objects or make your app backwards-compatible?
new Date()is your tried-and-true companion. - Dealing with
Dates in different timezones or have complex calendar operations?Calendar.getInstance().getTime()packs the tool belt you need.
When to use what?
Crunch time
Use System.currentTimeMillis() when you're crunching number-crunching code, and every millisecond wasted is a dime lost!
Need the package deal?
Invoke new Date() when you're out shopping for an actual date for your next big-time event (like logging or scheduled tasks).
The calendar whiz
Calendar is the nerdy brainiac of the date/time world, ideal when you're twisting and turning with complex date arithmetic and timezone gymnastics.
The new kid with the cool bike
For anyone coding on the cool side of Java 8, shake hands with java.time or Joda Time - they're the hipsters of date/time handling.
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