jdk8 refactor

refactor.java

// before

private String getExpandValuesFromSet (Set<String> valueSet, Boolean surroundValueWithQuotes) {
  StringBuilder expansionValuesString = new StringBuilder(" (");

  Iterator<String> valueIterator = valueSet.iterator();
  if (valueIterator.hasNext()) {
    String value = valueIterator.next();
    if (surroundValueWithQuotes) {
      expansionValuesString.append("'" + value + "'");
    } else {
      expansionValuesString.append(value);
    }

    while (valueIterator.hasNext()) {
      String nextValue = valueIterator.next();
      expansionValuesString.append(",");
      if (surroundValueWithQuotes) {
          expansionValuesString.append("'" + nextValue + "'");
      } else {
          expansionValuesString.append(nextValue);
      }
    }
  }
  expansionValuesString.append(")");
  return expansionValuesString.toString();
}
    
    
// after    
    
private StringJoiner getExpandValuesFromSet (Set<String> valueSet, Boolean surroundValueWithQuotes) {
    StringJoiner clause = new StringJoiner(", ", " (", ") ");
    Function<String, String> surrounder = 
            getQuoteSurrounder(surroundValueWithQuotes);
    valueSet.stream()
        .map(cleaner)
        .map(surrounder)
        .forEach(clause::add);
    return clause;
}

private Function<String, String> getQuoteSurrounder(boolean surround) {
    return surround ?
            s -> "'" + s + "'" :
            Function.identity();
}