java - Running TestNG tests in parallel -

i wanted run tests defined testng in parallel.

i have @dataprovider method contains list of ids

@beforeclass method gets every id, processing , stores result in map. there 1 @test method uses values present in map , performs validation.

i used following statement within xml:

<suite name="my suite" parallel="methods" thread-count="5"> 

i wanted run tests in parallel , map computed should not shared across thread. values should thread specific.

how should define such variable , use thread?