Java StringTokenizer, empty null tokens

Question

I am trying to split a string into 29 tokens..... stringtokenizer won't return null tokens. I tried string.split, but I believe I am doing something wrong:

String [] strings = line.split(",", 29);

sample inputs:

10150,15:58,23:58,16:00,00:00,15:55,23:55,15:58,00:01,16:03,23:58,,,,,16:00,23:22,15:54,00:03,15:59,23:56,16:05,23:59,15:55,00:01,,,,
10155,,,,,,,,,,,07:30,13:27,07:25,13:45,,,,,,,,,,,07:13,14:37,08:01,15:23
10160,10:00,16:02,09:55,16:03,10:06,15:58,09:48,16:07,09:55,16:00,,,,,09:49,15:38,10:02,16:04,10:00,16:00,09:58,16:01,09:57,15:58,,,,

Solution 1

If you want the trailing empty strings to be kept, but you don't want to give a magic number for maximum, use a negative limit:

line.split(",", -1)

If line.equals("a,,c"), then line.split(",", -1)[1].isEmpty(); it's not null. This is because when "," is the delimiter, then ",," has an empty string between the two delimiters, not null.

---

Example:

Using the explanation above, consider the following example: ",,"

Although you might expect ",", null, and ",".

The actual result is ",", "" and ","

---

null

split

null

s == null

s.isEmpty()

See also

• Java String.indexOf and empty strings

Solution 2

Use StringUtils.splitPreserveAllTokens() in Apache Commons Lang library

Solution 3

If you want empty tokens to be retained string.split won't work satisfactorily. StringTokenizer will also no work. I have come with following method, which might be helpful for you

public static String[] splitTotokens(String line, String delim){
  String s = line;
  int i = 0;

  while (s.contains(delim)) {
  s = s.substring(s.indexOf(delim) + delim.length());
      i++;
  }
  String token = null;
  String remainder = null;
  String[] tokens = new String[i];

  for (int j = 0; j < i; j++) {
    token = line.substring(0, line.indexOf(delim));
    //System.out.print("#" + token + "#");
    tokens[j] = token;
    remainder = line.substring(line.indexOf(delim) + delim.length());
    //System.out.println("#" + remainder + "#");
    line = remainder;
    }

  return tokens;`  
 }

Comments

[user69514]

I was checking things wrong. 29 actually works. -1 does too. Thansk

[user69514]

yeah I noticed that. I just check if the string is empty rather than null.

[polygenelubricants]

@user69: use isEmpty() if Java6, use length() == 0 otherwise. Don't use equals("").