[SDK Optimization] Multiple SimpleDateFormat initialization in CarbonReader

[zhangboren93]

I found that reading carbon files from CarbonReader takes long time in "SimpleDateFormat.", see attached file for output of
profiling.

carbondata/sdk/sdk/src/main/java/org/apache/carbondata/sdk/file/CarbonReader.java

Line 207 in 4b8846d

SimpleDateFormat dateFormat = new SimpleDateFormat(carbonDateFormat);

I wonder if it is OK if we add some lazy initialization to SimpleDateFormat in the class, and if so should it support multi-threading.

profile.zip

[prajwalbandak]

hey @zhangboren93 , Can you please assign to me and please explain the issue?