code: public String toQueryString(Criteria criteria, CriteriaQueryBuilder queryBuilder) {
      
      // fallback for empty criteria list
      if( criterionList.isEmpty() ) {
        return "1=1";
      }
      
      // build junction
      StringBuilder builder = new StringBuilder();
      builder.append("(");
      
      Iterator<Criterion> critIter = criterionList.iterator();
      while( critIter.hasNext() ) {
        
        // add JPQL string
        builder.append( critIter.next().toQueryString(criteria, queryBuilder) );
        
        // add op if more entries follow
        if( critIter.hasNext() ) {
          builder.append(' ').append(op).append(' ');
        }
        
      }
      
      builder.append(")");
      return builder.toString();
    
    }
docs: /*
  @see org.criteria4jpa.criterion.Criterion#toQueryString(org.criteria4jpa.Criteria, org.criteria4jpa.impl.CriteriaQueryBuilder)