Java String replaceAll - works in a wierd way for \

Question

I have a string like this :

My word is "I am busy" message

Now when I assign this string to a pojo field, I get is escaped as below :

String test = "My word is \"I am busy\" message";

I have some other data in which I want something to be replaced by above string :

Let say my base string is :

String s = "There is some __data to be replaced here";

Now I when I use replaceAll :

String s1 = s.replaceAll("__data", test);
System.out.println(s1);

This returns me the output as :

There is some My word is "I am busy" message to be replaced here

Why that "\" is not appearing in after I replace. Do I need to escape it 2 times?

Also when use it like this :

String test = "My word is \\\"I am busy\\\" message";

then also it gives the same output as :

There is some My word is "I am busy" message to be replaced here

My expected output is :

There is some My word is \"I am busy\" message to be replaced here

possible duplicate of [Why String.ReplaceAll() in java requires 4 slashes "\\\\" in regex to actually replace "\"?](http://stackoverflow.com/questions/18875852/why-string-replaceall-in-java-requires-4-slashes-in-regex-to-actually-r) — PM 77-1, Apr 15 '15 at 05:20
The "\" in the original `String` are there so the compiler ignores them, if you print the original `String` you will get `My word is "I am busy" message` — MadProgrammer, Apr 15 '15 at 05:23

Rahul Tripathi · Accepted Answer · 2015-04-15T05:25:34.933

Try this:

String test = "My word is \\\\\"I am busy\\\\\" message";
String s = "There is some __data to be replaced here";
System.out.println(s.replaceAll("__data", test));

To get the \ in your output you need to use \\\\\

From the docs:

Note that backslashes () and dollar signs ($) in the replacement string may cause the results to be different than if it were being treated as a literal replacement string; see Matcher.replaceAll. Use Matcher.quoteReplacement(java.lang.String) to suppress the special meaning of these characters, if desired.

So you can use Matcher.quoteReplacement(java.lang.String)

String test = "My word is \"I am busy\" message";
String s = "There is some __data to be replaced here";
System.out.println(s.replaceAll("__data", test), Matcher.quoteReplacement(test));

I don't have control over adding backslash, I am getting the data from outside. Do you mean I escape it twice? — Abubakkar, Apr 15 '15 at 05:22

Avinash Raj · Answer 2 · 2015-04-15T05:25:07.090

3

You need to use four backslashes to print a single backslash.

String test = "My word is \\\\\"I am busy\\\\\" message";
String s = "There is some __data to be replaced here";
System.out.println(s.replaceAll("__data", test));

OR

String test = "My word is \"I am busy\" message";
String s = "There is some __data to be replaced here";
System.out.println(s.replaceAll("__data", test.replace("\"", "\\\\\"")));

Output:

There is some My word is \"I am busy\" message to be replaced here

edited Apr 15 '15 at 05:25

answered Apr 15 '15 at 05:20

Avinash Raj

172,303
28
230
274

I don't have control over adding backslash, I am getting the data from outside. Do you mean I escape it twice? – Abubakkar Apr 15 '15 at 05:22

Java String replaceAll - works in a wierd way for \

2 Answers2