UbuntuでJava 8をデフォルトで使おうと思うと、alternativesの値を変更する必要があると思うけど、update-alternatives -allで確認すると結構あるのでまとめておく。たとえば、/usr/lib/jvm/jdk1.8.0にJava 8を置いたら以下の感じ。
sudo update-alternatives --install "/usr/bin/ControlPanel" "ControlPanel" "/usr/lib/jvm/jdk1.8.0/jre/bin/ControlPanel" 1 sudo update-alternatives --install "/usr/bin/appletviewer" "appletviewer" "/usr/lib/jvm/jdk1.8.0/bin/appletviewer" 1 sudo update-alternatives --install "/usr/bin/extcheck" "extcheck" "/usr/lib/jvm/jdk1.8.0/bin/extcheck" 1 sudo update-alternatives --install "/usr/bin/idlj" "idlj" "/usr/lib/jvm/jdk1.8.0/bin/idlj" 1 sudo update-alternatives --install "/usr/bin/jar" "jar" "/usr/lib/jvm/jdk1.8.0/bin/jar" 1 sudo update-alternatives --install "/usr/bin/jarsigner" "jarsigner" "/usr/lib/jvm/jdk1.8.0/bin/jarsigner" 1 sudo update-alternatives --install "/usr/bin/java" "java" "/usr/lib/jvm/jdk1.8.0/jre/bin/java" 1 sudo update-alternatives --install "/usr/bin/javac" "javac" "/usr/lib/jvm/jdk1.8.0/bin/javac" 1 sudo update-alternatives --install "/usr/bin/javadoc" "javadoc" "/usr/lib/jvm/jdk1.8.0/bin/javadoc" 1 sudo update-alternatives --install "/usr/bin/javafxpackager" "javafxpackager" "/usr/lib/jvm/jdk1.8.0/bin/javafxpackager" 1 sudo update-alternatives --install "/usr/bin/javah" "javah" "/usr/lib/jvm/jdk1.8.0/bin/javah" 1 sudo update-alternatives --install "/usr/bin/javap" "javap" "/usr/lib/jvm/jdk1.8.0/bin/javap" 1 sudo update-alternatives --install "/usr/bin/javaws" "javaws" "/usr/lib/jvm/jdk1.8.0/jre/bin/javaws" 1 sudo update-alternatives --install "/usr/bin/jcmd" "jcmd" "/usr/lib/jvm/jdk1.8.0/bin/jcmd" 1 sudo update-alternatives --install "/usr/bin/jconsole" "jconsole" "/usr/lib/jvm/jdk1.8.0/bin/jconsole" 1 sudo update-alternatives --install "/usr/bin/jcontrol" "jcontrol" "/usr/lib/jvm/jdk1.8.0/jre/bin/jcontrol" 1 sudo update-alternatives --install "/usr/bin/jdb" "jdb" "/usr/lib/jvm/jdk1.8.0/bin/jdb" 1 sudo update-alternatives --install "/usr/bin/jexec" "jexec" "/usr/lib/jvm/jdk1.8.0/jre/lib/jexec" 1 sudo update-alternatives --install "/usr/bin/jhat" "jhat" "/usr/lib/jvm/jdk1.8.0/bin/jhat" 1 sudo update-alternatives --install "/usr/bin/jinfo" "jinfo" "/usr/lib/jvm/jdk1.8.0/bin/jinfo" 1 sudo update-alternatives --install "/usr/bin/jmap" "jmap" "/usr/lib/jvm/jdk1.8.0/bin/jmap" 1 sudo update-alternatives --install "/usr/bin/jps" "jps" "/usr/lib/jvm/jdk1.8.0/bin/jps" 1 sudo update-alternatives --install "/usr/bin/jrunscript" "jrunscript" "/usr/lib/jvm/jdk1.8.0/bin/jrunscript" 1 sudo update-alternatives --install "/usr/bin/jsadebugd" "jsadebugd" "/usr/lib/jvm/jdk1.8.0/bin/jsadebugd" 1 sudo update-alternatives --install "/usr/bin/jstack" "jstack" "/usr/lib/jvm/jdk1.8.0/bin/jstack" 1 sudo update-alternatives --install "/usr/bin/jstat" "jstat" "/usr/lib/jvm/jdk1.8.0/bin/jstat" 1 sudo update-alternatives --install "/usr/bin/jstatd" "jstatd" "/usr/lib/jvm/jdk1.8.0/bin/jstatd" 1 sudo update-alternatives --install "/usr/bin/jvisualvm" "jvisualvm" "/usr/lib/jvm/jdk1.8.0/bin/jvisualvm" 1 sudo update-alternatives --install "/usr/bin/keytool" "keytool" "/usr/lib/jvm/jdk1.8.0/jre/bin/keytool" 1 sudo update-alternatives --install "/usr/lib/mozilla/plugins/libnpjp2.so" "libnpjp2.so" "/usr/lib/jvm/jdk1.8.0/jre/lib/amd64/libnpjp2.so" 1 sudo update-alternatives --install "/usr/lib/mozilla/plugins/libjavaplugin.so" "mozilla-javaplugin.so" "/usr/lib/jvm/jdk1.8.0/jre/lib/amd64/libnpjp2.so" 1 sudo update-alternatives --install "/usr/bin/native2ascii" "native2ascii" "/usr/lib/jvm/jdk1.8.0/bin/native2ascii" 1 sudo update-alternatives --install "/usr/bin/orbd" "orbd" "/usr/lib/jvm/jdk1.8.0/jre/bin/orbd" 1 sudo update-alternatives --install "/usr/bin/pack200" "pack200" "/usr/lib/jvm/jdk1.8.0/jre/bin/pack200" 1 sudo update-alternatives --install "/usr/bin/policytool" "policytool" "/usr/lib/jvm/jdk1.8.0/jre/bin/policytool" 1 sudo update-alternatives --install "/usr/bin/rmic" "rmic" "/usr/lib/jvm/jdk1.8.0/bin/rmic" 1 sudo update-alternatives --install "/usr/bin/rmid" "rmid" "/usr/lib/jvm/jdk1.8.0/jre/bin/rmid" 1 sudo update-alternatives --install "/usr/bin/rmiregistry" "rmiregistry" "/usr/lib/jvm/jdk1.8.0/jre/bin/rmiregistry" 1 sudo update-alternatives --install "/usr/bin/schemagen" "schemagen" "/usr/lib/jvm/jdk1.8.0/bin/schemagen" 1 sudo update-alternatives --install "/usr/bin/serialver" "serialver" "/usr/lib/jvm/jdk1.8.0/bin/serialver" 1 sudo update-alternatives --install "/usr/bin/servertool" "servertool" "/usr/lib/jvm/jdk1.8.0/jre/bin/servertool" 1 sudo update-alternatives --install "/usr/bin/tnameserv" "tnameserv" "/usr/lib/jvm/jdk1.8.0/jre/bin/tnameserv" 1 sudo update-alternatives --install "/usr/bin/unpack200" "unpack200" "/usr/lib/jvm/jdk1.8.0/jre/bin/unpack200" 1 sudo update-alternatives --install "/usr/bin/wsgen" "wsgen" "/usr/lib/jvm/jdk1.8.0/bin/wsgen" 1 sudo update-alternatives --install "/usr/bin/wsimport" "wsimport" "/usr/lib/jvm/jdk1.8.0/bin/wsimport" 1 sudo update-alternatives --install "/usr/bin/xjc" "xjc" "/usr/lib/jvm/jdk1.8.0/bin/xjc" 1
そして、
sudo update-alternatives --all
で全部の設定が聞かれるので対象箇所を変更しておく。