Can't seem to split String by new line regex

Question

I have this method, and it will not correctly add the split string to my list.

public static List<String> formatConfigMessages(FileConfiguration config, String key, boolean colour, Object... regex) {
    List<String> messages = new ArrayList<>();
    if (config.isList(key)) {
        config.getStringList(key).forEach(message -> {
            if (message.contains("\\n")) {
                Collections.addAll(messages, message.split("\\r\\n|\\n|\\r"));
            } else {
                messages.add(message);
            }
        });
    } else {
        String message = config.getString(key);
        if (message.contains("\\n")) {
            Collections.addAll(messages, message.split("\\r\\n|\\n|\\r"));
        } else {
            messages.add(message);
        }
    }
    return messages.stream().map(message -> formatMessage(message, colour, regex)).collect(Collectors.toList());
}

For a bit of context, this method is used to format configurable messages for my SpigotMC plugin. The method takes 4 parameters:

FileConfiguration - A class made to simplify the use of YAML configuration files.
String - the key of the message (can be indexed with '.', either side of the '.' represents a different level of the YAML file).
Boolean - whether or not reserved characters in the string should be converted into coloured characters (colours can only be seen by the client)
Object... - some patterns, etc.) <name> to be replaced with the following value in the array.

That is the chunk of code that won't work. Initially, I attempted to set the regex as \n, but that didn't return a list. I assumed this was because it was searching for already parsed new lines rather than the '\n' stream of characters. So I changed my regex to \n, which still didn't work. I search the internet and found in this post that I should use the regex \\r\\n as well as \\n because \r is used on Windows systems. This again did not work, and I keep getting 1 string with the \n still inside.

Do you have newline symbols at all or 2-char combinations of ``\`` + `n`? Also, to match any line break, you may use `\R` - `.split("\\R+")`. — Wiktor Stribiżew, Apr 14 '17 at 14:21
@WiktorStribiżew what do you mean by newline symbols? Anyway, I'm using the '\n' combination. However, I'm making this for a client and I want it to work with any newline value they use. — Victor Olaitan, Apr 14 '17 at 14:23
A newline symbol is a decimal `10` char. Google ASCII table. In a Java string literal, `"\n"` defines a newline. A `"\\n"` defines two char sequence, ``\`` and `n`. — Wiktor Stribiżew, Apr 14 '17 at 14:25
I think I should ask you this question. Did `.split("\\R+")` work? If not, there are no literal line breaks in your input. — Wiktor Stribiżew, Apr 14 '17 at 14:28
Good, so there are no line breaks in the input. You cannot split with something that does not exist. — Wiktor Stribiżew, Apr 14 '17 at 14:33
Hold on. My last comment was referring to the unedited version of your previous comment. I am using line breaks in this format " \n " — Victor Olaitan, Apr 14 '17 at 15:39
I think he was clarifying whether the text literally contains "\n" or if it actually has a line break. — Salem, Apr 15 '17 at 16:24

score 1 · Answer 1 · edited May 23 '17 at 11:46

Here's why.

Regex has its own escape sequences, denoted with \\ (the escape sequence for \), since Java reserves \.

For example, \\w denotes any character in a word.

To split by "\n", you'll need \\\\n instead, because \\n in regex represents an actual line break, just as \n represents one in Java.

Example:

System.out.println(Arrays.toString("Hello\\nworld".split("\\\\n")));
System.out.println(Arrays.toString("Hello world\nwith newline".split("\\n")));
System.out.println(Arrays.toString("Hello world\nwith newline".split("\n")));
System.out.println(Arrays.toString("I won't\\nsplit".split("\\n")));

Prints:

[Hello, world]
[Hello world, with newline]
[Hello world, with newline] <-- Same effect as above
[I won't\nsplit]

Additionally, to handle all three line end types (though \r on its own is uncommon nowadays), use the regex \\\\r?\\\\n|\\\\r instead.

Can't seem to split String by new line regex

1 Answers1