ferro@void:~$ whereis java
java: /usr/bin/java /etc/java /usr/lib/java /usr/X11R6/bin/java /usr/bin/X11/java /usr/share/java /usr/share/man/man1/java.1.gz
ferro@void:~$ ls -l /usr/bin/java
lrwxrwxrwx 1 root root 22 2007-06-21 14:15 /usr/bin/java -> /etc/alternatives/java
ferro@void:~$ ls -l /etc/alternatives/ja
jar          java         java_vm      javaws.1.gz  
jar.1.gz     java.1.gz    javaws       
ferro@void:~$ ls -l /etc/alternatives/java
lrwxrwxrwx 1 root root 34 2007-06-21 14:15 /etc/alternatives/java -> /usr/lib/jvm/java-gcj/jre/bin/java
ferro@void:~$ java --help
Usage: gij [OPTION] ... CLASS [ARGS] ...