public ParameterTypeFile(String key,String description,boolean optional,String[] extensions){
  super(key,description,null);
  setOptional(optional);
  this.extensions=extensions;
}

public ParameterTypeFile ( String key , String description , boolean optional , String [ ] extensions ) { super ( key , description , null ) ; setOptional ( optional ) ; this . extensions = extensions ; }
creates a new parameter type for files with the given extension . if the extension is null no file filters will be used . if the parameter is not optional , it is set to be not expert .
