JVM SimpleDateFormat Kata

Challange

• Make SimpleDateFormat produce wrong results on multiple threads
• Create Thread safe SimpleDateFormat

HowTo run

mvn exec:java

Results

SimpleDateFormat without thrad safe checks
[ERROR] SimpleDateFormat thrown exception: java.util.concurrent.ExecutionException: java.lang.NumberFormatException: multiple points

ThreadSafe formatter
[OK] All dates are the same

Solution

• Creating ThreadLocal instance with SimpleDateFormat

ThreadLocal<DateFormat> threadDateFormat = ThreadLocal.withInitial(() -> new SimpleDateFormat(pattern));