Question

给出StringBuilder这种形式：

data_driven: [data-driven, web economy, leading, Fortune 500, knowledge-driven, pyramid-based, market-driven, capital-based, profit-driven, market-focused, bottom-line focused, new economy, Brazilian, European ], 
market_leaders: [market leaders, corporations, eCompanies, eBusinesses, web 2.0 corporations, virtual companies, virtual businesses, virtual eBusinesses, virtual eMonopolies, information workers ]

我需要在给定令牌（例如data_driven或market_leaders）后的括号内创建一个列表。

这是我的代码：

public List<String> getPhrases(StringBuilder fileContent, String token) {
StringReader reader = new StringReader(fileContent.toString());
BufferedReader br = new BufferedReader(reader);  
StreamTokenizer tokenizer = new StreamTokenizer(br);
List<String> list = new ArrayList<String>();
    try {
          while (tokenizer.nextToken() != StreamTokenizer.TT_EOF) {
            if (tokenizer.sval.equals(token)) {
              tokenizer.nextToken();  // skip the ":"
              tokenizer.nextToken(); // skip the "["
              do {
                tokenizer.nextToken();  // go to the first phrase
                String stuff = tokenizer.sval;
                list.add(stuff);
              } while (tokenizer.nextToken() == ',');
              break;
            }
          }
        } catch (IOException e) {
            e.printStackTrace();
        }
}

当我使用StringBuilder和令牌作为参数调用方法时，我会在该行获得NullPointerException：

if (tokenizer.sval.equals(token)) {

我已经打印出我的StringBuilder并且拥有我在调用方法时使用过的令牌。

有没有人知道为什么我会得到这个例外？

Answer 1

我可能会对这个问题采取不同的方法，我会首先隔离外部令牌;然后我会隔离“[”和“]”的内容然后我会使用StringTokenizer，即我会使用这种方法

// Static level, because it doesn't depend on outside state.
public static List<String> getPhrases(
    StringBuilder fileContent, String token) {
  // An output List.
  List<String> al = new ArrayList<String>();
  final int p1 = fileContent.indexOf(token);
  if (p1 >= 0) { // we have a "token"
    int pos1 = fileContent.indexOf("[", p1 + 1);
    if (pos1 >= 0) { // we have an open "["
      int pos2 = fileContent.indexOf("]", pos1 + 1);
      if (pos2 >= 0) { // we have a closing "]"
        String str = fileContent.substring(pos1 + 1,
            pos2);
        StringTokenizer st = new StringTokenizer(
            str, ","); // Now use a Tokenizer.
        while (st.hasMoreTokens()) {
          String s = st.nextToken();
          if (s != null) { // Don't trim a null!
            al.add(s.trim());
          } else { // You may not want this...
            al.add("");
          }
        }
      }
    }
  }
  // Return that output List.
  return al;
}

使用StreamTokenizer的NullPointerException

1 个答案: