Cannot remove newline characters (\n) in a java String. is it even possible?

Question

Basically, all I'm trying to do is remove the newline character from a String in Java. I've looked at dozens of posts asking similar questions and they all say the same thing, but none of them seem to work for me. Here is all the code I have 3 lines:

    String text = "\\n          texttexttext     \\n";
    text = text.replaceAll("\\n", "");
    System.out.println(text);

That string is similar to what I'm actually trying to use, but even with this one I can't find the newline character and replace it. The replaceAll just won't see it and I don't know why.

I've tried plenty of other things too like

    text = text.replaceAll("\\n", "").replaceAll("\\r", "");

or

    text = text.replaceAll("\\r\\n|\\r|\\n", " ");

but nothing can even find the character. I haven't even been able to find it using Regex Pattern and Matcher objects. The only thing slightly unusual I'm doing is doing it in a Junit Test bean, but I cannot believe that would do anything.

Answer 1

You don't have a newline character in your original text. You have escaped the backslash, not the n, so you have actual backslash \ and n characters in your text string.

You did have to escape the backslash character in your regular expression, but not in your literal string text.

If you initialize text as "\n texttexttext \n", then it will find and replace those newlines as expected.

Answer 2

String newLine = System.getProperty("line.separator")
System.out.println(newLine.contains("\n")); // this is a new line
System.out.println(newLine.contains("\\n"));

output:

true
false

Answer 3

As commented by Jon Lin

Your example text does not actually talk about newlines - \\n is the string \n.

The other fallacy is that replaceAll expects a regular expression as the first input. So \\n is actually replaced to \n as \ is the escaping character, which is then interpreted as a newline character - case of double escaping, thus in your input text \\ is not matched.

If you try

text = text.replaceAll("\\\\n", "");

At least you get the expected result, as it's both a Java string and a regular expression both interpret \ as escaping character.