public ExpressionType negate(){
  if (isNegated()) {
    return new ExpressionType(typeString.replace(SUFFIX_NEGATED,""));
  }
 else {
    return new ExpressionType(typeString + SUFFIX_NEGATED);
  }
}

public ExpressionType negate ( ) { if ( isNegated ( ) ) { return new ExpressionType ( typeString . replace ( SUFFIX_NEGATED , "" ) ) ; } else { return new ExpressionType ( typeString + SUFFIX_NEGATED ) ; } }
negate the type . this are the two typical cases : ver - > ver - neg ver - neg - > ver
