Debian packages that has this binary:
/usr/lib/jvm/java-1.5.0-gcj-4.8-amd64/bin/appletviewer
/usr/lib/jvm/java-1.5.0-gcj-4.9-amd64/bin/appletviewer
/usr/lib/debug/usr/lib/jvm/java-7-openjdk-amd64/bin/appletviewer
/usr/lib/jvm/java-7-openjdk-amd64/bin/appletviewer