Very weird! I am also getting same issue when I build my smack project early today but the build I made yesterday is working fine without any exceptions!
I am also using Smack 4.2.0 and also tried 4.2.1-SNAPSHOT but no luck
compile "org.igniterealtime.smack:smack-android-extensions:4.2.0"
compile "org.igniterealtime.smack:smack-experimental:4.2.0"
compile(“org.igniterealtime.smack:smack-tcp:4.2.0”)
java.lang.ExceptionInInitializerError
at de.measite.minidns.DNSName.from(DNSName.java:287)
at de.measite.minidns.dnssec.DNSSECClient.(DNSSECClient.java:48)
at de.measite.minidns.hla.DnssecResolverApi.(DnssecResolverApi.java:47)
at de.measite.minidns.hla.DnssecResolverApi.(DnssecResolverApi.java:38)
at de.measite.minidns.hla.DnssecResolverApi.(DnssecResolverApi.java:31)
at org.jivesoftware.smack.util.dns.minidns.MiniDnsResolver.(MiniDnsResolve r.java:54)
at java.lang.Class.classForName(Native Method)
at java.lang.Class.forName(Class.java:400)
at org.jivesoftware.smack.SmackInitialization.loadSmackClass(SmackInitialization.j ava:218)
at org.jivesoftware.smack.SmackInitialization.parseClassesToLoad(SmackInitializati on.java:198)
at org.jivesoftware.smack.SmackInitialization.processConfigFile(SmackInitializatio n.java:168)
at org.jivesoftware.smack.SmackInitialization.processConfigFile(SmackInitializatio n.java:153)
at org.jivesoftware.smack.SmackInitialization.(SmackInitialization.java:11 9)
at org.jivesoftware.smack.SmackConfiguration.getVersion(SmackConfiguration.java:96 )
at org.jivesoftware.smack.provider.ProviderManager.(ProviderManager.java:1 21)
at org.jivesoftware.smack.provider.ProviderManager.addExtensionProvider(ProviderMa nager.java:259)
Caused by: java.lang.IllegalArgumentException: Invalid input to toASCII: .
at java.net.IDN.toASCII(IDN.java:112)
at java.net.IDN.toASCII(IDN.java:134)
at de.measite.minidns.idna.DefaultIdnaTransformator.toASCII(DefaultIdnaTransformat or.java:19)
at de.measite.minidns.idna.MiniDnsIdna.toASCII(MiniDnsIdna.java:18)
at de.measite.minidns.DNSName.(DNSName.java:103)
at de.measite.minidns.DNSName.(DNSName.java:59)
Caused by: Found zero length lable after NamePrep… line: 0. preContext: . postContext:
at android.icu.impl.IDNA2003.convertToASCII(IDNA2003.java:185)
at android.icu.impl.IDNA2003.convertIDNToASCII(IDNA2003.java:275)
at android.icu.text.IDNA.convertIDNToASCII(IDNA.java:652)