public void add(Attr attr){
  if (attr == null)   return;
  Attr attr1=findAttribute(attr.getName());
  if (attr1 == null) {
    _attrs.add(attr);
  }
 else {
    attr1.addValues(attr.getStringValues());
  }
}

public void add ( Attr attr ) { if ( attr == null ) return ; Attr attr1 = findAttribute ( attr . getName ( ) ) ; if ( attr1 == null ) { _attrs . add ( attr ) ; } else { attr1 . addValues ( attr . getStringValues ( ) ) ; } }
add one attribute to the attrset the attribute should have only string values
