How do i see what alternatives are maintained for a command in ubuntu?

[amurleopard]

update-alternatives man page: http://bit.ly/2rEE4NT

Display the alternatives for java.

$ update-alternatives --display java
java - manual mode
  link currently points to /usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java
/usr/lib/jvm/java-7-openjdk-amd64/jre/bin/java - priority 1071
  slave java.1.gz: /usr/lib/jvm/java-7-openjdk-amd64/jre/man/man1/java.1.gz
/usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java - priority 1069
  slave java.1.gz: /usr/lib/jvm/java-8-openjdk-amd64/jre/man/man1/java.1.gz
Current 'best' version is '/usr/lib/jvm/java-7-openjdk-amd64/jre/bin/java'.

On other linux systems you may find the command as just alternatives.