相当于具有多个字符分隔符的StringTokenizer

Question

我尝试将一个字符串拆分为标记.

令牌分隔符不是单个字符,某些分隔符包含在其他分隔符中(例如&和&&),我需要将分隔符作为标记返回.
StringTokenizer无法处理多个字符分隔符.我认为它可以使用String.split,但无法猜出适合我需要的神奇正则表达式.

任何的想法 ？

例:

Token delimiters: "&", "&&", "=", "=>", " "  
String to tokenize: a & b&&c=>d  
Expected result: an string array containing "a", " ", "&", " ", "b", "&&", "c", "=>", "d"

---编辑---
感谢大家的帮助,Dasblinkenlight为我提供了解决方案.以下是我在他的帮助下写的"随时可用"代码:

private static String[] wonderfulTokenizer(String string, String[] delimiters) {
  // First, create a regular expression that matches the union of the delimiters
  // Be aware that, in case of delimiters containing others (example && and &),
  // the longer may be before the shorter (&& should be before &) or the regexpr
  // parser will recognize && as two &.
  Arrays.sort(delimiters, new Comparator<String>() {
    @Override
    public int compare(String o1, String o2) {
      return -o1.compareTo(o2);
     }
  });
  // Build a string that will contain the regular expression
  StringBuilder regexpr = new StringBuilder();
  regexpr.append('(');
  for (String delim : delimiters) { // For each delimiter
    if (regexpr.length() != 1) regexpr.append('|'); // Add union separator if needed
    for (int i = 0; i < delim.length(); i++) {
      // Add an escape character if the character is a regexp reserved char
      regexpr.append('\\');
      regexpr.append(delim.charAt(i));
    }
  }
  regexpr.append(')'); // Close the union
  Pattern p = Pattern.compile(regexpr.toString());

  // Now, search for the tokens
  List<String> res = new ArrayList<String>();
  Matcher m = p.matcher(string);
  int pos = 0;
  while (m.find()) { // While there's a delimiter in the string
    if (pos != m.start()) {
      // If there's something between the current and the previous delimiter
      // Add it to the tokens list
      res.add(string.substring(pos, m.start()));
    }
    res.add(m.group()); // add the delimiter
    pos = m.end(); // Remember end of delimiter
  }
  if (pos != string.length()) {
    // If it remains some characters in the string after last delimiter
    // Add this to the token list
    res.add(string.substring(pos));
  }
  // Return the result
  return res.toArray(new String[res.size()]);
}

如果您通过仅创建一次Pattern来标记许多字符串,则可以进行优化.

Answer 1

您可以使用Pattern和一个简单的循环来实现您正在寻找的结果：

List<String> res = new ArrayList<String>();
Pattern p = Pattern.compile("([&]{1,2}|=>?| +)");
String s = "s=a&=>b";
Matcher m = p.matcher(s);
int pos = 0;
while (m.find()) {
    if (pos != m.start()) {
        res.add(s.substring(pos, m.start()));
    }
    res.add(m.group());
    pos = m.end();
}
if (pos != s.length()) {
    res.add(s.substring(pos));
}
for (String t : res) {
    System.out.println("'"+t+"'");
}

这会产生以下结果：

's'
'='
'a'
'&'
'=>'
'b'