I posted it without being able to test. Now I am back home and can test, and it works for me as shown in this session under the Perl debugger:

  DB<1> $line = 'root 30145 1 0 Jan30 ? 00:09:01 /root/java/app/java_a
+pp_1Rule_java_app_2Rule.java --javaproc';

  DB<2> $id = $1 if $line =~ /(\w+)\.java\s/;

  DB<3> print $id;
java_app_1Rule_java_app_2Rule
[download]

And, BTW, I don 't see why I received a downvote for a solution that works.