There is problematic rendering compared to Browsers/Windows Notepad vs JDK for
Consonant + U+DCA (VIRAMA) + U+200D(ZWJ) + U+0DBB ra (or U+0DBA ya) + Vowel
For instance:
 U+0DC1(sha)+ U+0DCA + U+200D + U+0DBB ra + U+0DD3(ii)
 U+0D9a(ka) + U+0DCA + U+200D + U+0DBB ra + U+0DD2(i)
 U+0D9a(ka) + U+0DCA + U+200D + U+0DBB ra + U+0DD3(ii)
 U+0D9b(kha)+ U+0DCA + U+200D + U+0DBA ya + U+0DCF(aa)
 U+0Da7(tta)+ U+0DCA + U+200D + U+0DBB ra + U+0DDA(ee)
 U+0Db6(ba) + U+0DCA + U+200D + U+0DBB ra + U+0DD0(ae)

(Note: the opentype engine replacement in JDK9, does not affect
Sinhala rendering. e.g. JDK8 and JDK9 renders same).

References :
See https://en.wikipedia.org/wiki/Sinhalese_alphabet#Consonant_conjuncts
kra case is 2nd and 3rd case.

https://www.microsoft.com/typography/OpenTypeDev/sinhala/intro.htm
Rakaaraansaya U+0D9A U+0DCA U+200D U+0DBB
abvs image 2nd sample shows the above 2nd case.