Calling IDN.toASCII with non-ascii String arg. and IDN.USE_STD3_ASCII_RULES option is set.
Please try to run IDNTest.java attached.
slc00snz% which java
/java/re/jdk/8/latest/binaries/solaris-x64/bin/java
slc00snz% java IDNTest (non-ascii value such as ���������)
hostname = ���������
Exception in thread "main" java.lang.IllegalArgumentException: Contains
non-LDH characters
at java.net.IDN.toASCIIInternal(IDN.java:275)
at java.net.IDN.toASCII(IDN.java:118)
at IDNTest.main(IDNTest.java:23)
slc00snz%
javax.net.ssl.SNIHostName use it and throw exception when hostname is non-ascii.