Those class files are generated if in the source code there're inner classes:

example:

class A {
  class B {}
}

will generate A.class and A$B.class

if you use anonymous inner classes you get A$1.class and so on..

example:

class A {
    Object o = new Object() {};
}

will generate A.class and A$1.class

You cannot cancel their generation: it's the way the java compilation handle inner classes. Every compiler java compliant must use the same inner-class handling (even if in Unix Systems it can be a problem, because "$" is a special character for common shells).