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,,,,

Community · Accepted Answer · 2017-05-23 11:59:52Z

16

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 ","

If you want null instead of empty strings in the array returned by split, then you'd have to manually scan the array and replace them with null. I'm not sure why s == null is better than s.isEmpty(), though.

3 Comments

user69514 Over a year ago

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

user69514 Over a year ago

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

polygenelubricants Over a year ago

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

Thomas Auinger · Accepted Answer · 2013-07-12 13:18:43Z

5

Use StringUtils.splitPreserveAllTokens() in Apache Commons Lang library

answered Jul 12, 2013 at 13:18

Thomas Auinger

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Comments

Sastrija · Accepted Answer · 2012-02-14 07:47:18Z

2

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;`  
 }

edited Feb 14, 2012 at 7:47

Sastrija

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answered Feb 14, 2012 at 5:15

Wasim

211 bronze badge

Comments

user2675617 · Accepted Answer · 2013-10-18 20:51:34Z

1

use this org.springframework.util.StringUtils

org.springframework.util.StringUtils.delimitedListToStringArray(data, delimit);

This class delivers some simple functionality provides easy-to-use methods to convert between delimited strings, such as CSV strings, and collections and arrays.

edited Oct 18, 2013 at 20:51

answered Oct 17, 2013 at 18:49

user2675617

2483 silver badges4 bronze badges

Comments

MC Emperor · Accepted Answer · 2012-10-28 01:46:05Z

If you want empty tokens to be retained string.split() won't work satisfactorily. StringTokenizer will also not 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;
}

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