How to get what my string was split by in Java and save it to a List?

Question

So I am splitting a string by line separators, but I also want to save what line separator was used to use later when putting the string back together. How can I do that?

String data = "Multi\n Line\r Text\n";
List<String> separators = new ArrayList<>();
String lines[] = data.split("\\r?\\n|\\r");
separators.add(???);

I honestly don't know how to capture that. Is it possible with String.Split? Or is there another way that I can go about doing this?

I'm initially getting the string from a File. Is there a way to get and save the line separators that way before converting it into a string?

Java's built-in split doesn't provide the character used to split, maybe try creating your own splitter — Raj, Nov 19 '18 at 02:40
Please check it https://stackoverflow.com/questions/521146/c-sharp-split-string-but-keep-split-chars-separators — WGSSAMINTHA, Nov 19 '18 at 02:44

score 0 · Answer 1 · answered Nov 19 '18 at 03:00

You can use StringTokenizer as a starting point:

    String data = "Multi\n Line\r Text\n and now a two-char \r\nline separator";
    StringTokenizer tokenizer = new StringTokenizer(data, "\n\r", true);
    List<String> tokensAndDelimiters = new ArrayList<>();
    while (tokenizer.hasMoreTokens()) {
        tokensAndDelimiters.add(tokenizer.nextToken());
    }
    tokensAndDelimiters.replaceAll((token) -> token.replace("\n", "\\n").replace("\r", "\\r"));
    System.out.println("tokensAndDelimiters = " + tokensAndDelimiters);

The output of the above code is:

tokensAndDelimiters = [Multi, \n,  Line, \r,  Text, \n,  and now a two-char , \r, \n, line separator]

The third StringTokenizer constructor argument indicates to return delimiters as tokens. I'm only replacing the line separator characters so that they print out clearly. One thing to note is that if you have a typical windows line separator ("\r\n"), this will come out as two tokens because StringTokenizer only deals with single character delimiters.

Hmm, not sure if I'll be able to use this or not. Do you know if there is a way to do this through the Scanner or through the File class? — Dtb49, Nov 19 '18 at 20:43

Kartik · Answer 2 · 2018-11-20T02:35:41.990

0

String data = "Multi\n Line\r Text\n";
List<String> separators = new ArrayList<>(Arrays.asList(data.split("[[^\\r?\\n]&&[^\\r]]+")));
separators.remove(0); // first element is an empty string
String lines[] = data.split("\\r?\\n|\\r");

//reconstruction
for (int i = 0; i < lines.length; i++) {
    System.out.print(lines[i] + StringEscapeUtils.escapeJava(separators.get(i)).trim());
}

Output

Multi\n Line\r Text\n

edited Nov 20 '18 at 02:35

answered Nov 19 '18 at 03:22

Kartik

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I thought that the line breaks would need to be printed first not the other way around? How does this work? – Dtb49 Nov 19 '18 at 20:41
@Dtb49 I have updated the answer, please check again – Kartik Nov 20 '18 at 02:36

How to get what my string was split by in Java and save it to a List?

2 Answers2