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Creating SimpleDateFormat is expensive. Don’t use this unless it’s done seldom.
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OK if you can live with a bit of blocking. Use if formatDate() is not used much.
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Fastest option IF you reuse threads (thread pool). Uses more memory than 2. and has higher startup overhead.
For applications both 2. and 3. are viable options. Which is best for your case depends on your use case. Beware of premature optimization. Only do it if you believe this is an issue.
For libraries that would be used by 3rd party I’d use option 3.