java replaceAll not working for \n characters

Question

I have a string like this: John \n Barber now I want to replace \n with actual new line character so it will become

John

Barber

this is my code for this

replaceAll("\\n", "\n");

but it is not working and giving me same string John \n Barber

i think use replaceAll("\\\\n","\\n"); – gifpif Sep 18 '13 at 06:38 — gifpif, Sep 18 '13 at 06:38

Avi · Accepted Answer · 2015-06-01T07:58:07.397

31

You need to do:

replaceAll("\\\\n", "\n");

The replaceAll method expects a regex in its first argument. When passing 2 \ in java string you actually pass one. The problem is that \ is an escape char also in regex so the regex for \n is actualy \\n so you need to put an extra \ twice.

edited Jun 01 '15 at 07:58

answered Sep 18 '13 at 06:38

Avi

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nhahtdh · Answer 2 · 2013-09-18T06:45:57.457

4

Since \n (or even the raw new line character U+000A) in regex is interpreted as new line character, you need \\n (escape the \) to specify slash \ followed by n.

That is from the regex engine's perspective.

From the compiler's perspective, in Java literal string, you need to escape \, so we add another layer of escaping:

String output = inputString.replaceAll("\\\\n", "\n");
//                                      \\n      U+000A

edited Sep 18 '13 at 06:45

answered Sep 18 '13 at 06:39

nhahtdh

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when i tried this way its working,String x="x\ny"; String y=x.replaceAll("\\n", "\n"); System.out.println(y); – SpringLearner Sep 18 '13 at 06:44
@javaBeginner: Your original string contains the new line already. – nhahtdh Sep 18 '13 at 06:45
isnt this same way that of OP? – SpringLearner Sep 18 '13 at 06:46
@javaBeginner: No. OP's raw string contains a ``\`` followed by `n`, which means in Java literal, it would be `"something\\nsomething"` – nhahtdh Sep 18 '13 at 06:47
I am confused,still +1 for this answer – SpringLearner Sep 18 '13 at 06:48
@javaBeginner: OP's string contains ``\`` followed by an `n`. That is the difference here. If you want to make it clear, try to write a program that take input from command prompt, and use the replaceAll on it. – nhahtdh Sep 18 '13 at 06:49

score 3 · Answer 3 · answered Sep 18 '13 at 06:39

3

You need to escape \ character. So try

replaceAll("\\\\n", "\n");

answered Sep 18 '13 at 06:39

Rafi Kamal

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score 3 · Answer 4 · answered Sep 18 '13 at 06:41

3

replaceAll is using Regular Expressions, you can use replace which will also replace all '\n':

replace("\\\\n", "\n");

answered Sep 18 '13 at 06:41

stan

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java replaceAll not working for \n characters

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