Replacing string with "\" character in java

Question

I am matching a pattern which is a string "test" in sentence "you are test" and replace it with "test\".

StringBuffer sb = new StringBuffer();
Pattern pattern = Pattern.compile("test", Pattern.CASE_INSENSITIVE);
Matcher matcher = pattern.matcher("you are test");
while (matcher.find()) {
matcher.appendReplacement(sb, "test\"));
            }
matcher.appendTail(sb);
replacementString = sb.toString();

The issue is in the statement matcher.appendReplacement(sb, "test\")); where "\" is considered as special character and replacement is not performed.

Please share your thoughts on how overcome this scenario and how to replace with a "\" in the string.

try following? matcher.appendReplacement(sb, "<test\\>"));

noonecares
– noonecares

2013-02-15 13:27:41 +00:00
Commented Feb 15, 2013 at 13:27 — noonecares
– noonecares, Commented Feb 15, 2013 at 13:27

Denys Séguret · Accepted Answer · 2013-02-15 13:33:48Z

6

To put a \ in a string literal in java, you have to escape it as \\.

But it's a little more complicated. See the javadoc :

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. Dollar signs may be treated as references to captured subsequences as described above, and backslashes are used to escape literal characters in the replacement string.

So you have to double-escape :

matcher.appendReplacement(sb, "test\\\\"));

edited Feb 15, 2013 at 13:33

answered Feb 15, 2013 at 13:28

Denys Séguret

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Comments

Bohemian · Accepted Answer · 2013-02-15 13:39:10Z

0

Why are you using all those lines of code, when one line will do the same thing:

String s = input.replaceAll("test", "$0\\\\");

Note the use of $0 to back-reference the whole match, and the double-double backslash to create a literal regex backslash.

answered Feb 15, 2013 at 13:39

Bohemian♦

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