public void addGroup ( Group g ) { if ( immutable ) throw new IllegalStateException ( "Cant modify" ) ; if ( findGroup ( g . getShortName ( ) ) != null ) throw new IllegalArgumentException ( "Group name (" + g . getShortName ( ) + ") must be unique within Group " + getShortName ( ) ) ; groups . add ( g ) ; g . setParentGroup ( this ) ; // groups are a tree - only one parent }
Add a nested Group