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Replace backslash in string

I have a String in which I am trying to replace the number enclosed by two backslashes. For example: \10\ , I am trying to replace that with 10. I am currently using this regex to do that:
String texter = texthb.replaceAll("\\.+\\", "\\"+String.valueOf(pertotal + initper)+"\\");
This line is giving the following error:
Exception in thread "AWT-EventQueue-0" java.util.regex.PatternSyntaxException: Unexpected internal error near index 4
.+\
I know it is because the regex is wrong. What is the proper way to accomplish this? Thanks in advance.

Use four backslashes to match a single backslash character.
String texter = texthb.replaceAll("\\\\.+?\\\\", "\\\\"+String.valueOf(pertotal + initper)+"\\\\");

Regex - trying to match / \ | , or newline, error says invalid escape character

I'm actually trying to split a string on any of the following :
/
\
|
,
\n
Here's the regex I'm using, which gives the 'invalid escape character' error :
String delims = "[\\\\\|\\/\\n,]+";
String[] list1 = str1.split(delims);
I've tried a few more versions of this, trying to get the number of \'s right. What's the right way to do this?

"[/\\|\n,\\\\]+"
Some of these you need to double escape
/ matches /
\\| matches |
\n matches new line
, matches ,
\\\\ matches \

To create \ literal in regex engine you need to write it with four \ in string, so you have one \ extra
"[\\\\\|\\/\\n,]+";
1234^
here
Also you don't need to escape / in Java regex engine, and you don't need to pass \n as \\n (\n literal will be also accepted) you can so try with
String delims = "[\\\\|/\n,]+";

quotes in the java regular expressions

I get a String from the JSP, containing [", e.g.
["Bulgaria
I would like to replace all the [" occurrences for [', but I don't know exactly how to do it...
I just tried:
str = str.replaceAll("[\\\"", "['");
with the result
java.util.regex.PatternSyntaxException: Unclosed character class near index 2 [\"
and
html = html.replaceAll("[\"", "['");
with the result
java.util.regex.PatternSyntaxException: Unclosed character class near index 1 [" ^
any help will be appreciated

Try this:
str.replaceAll("\\[\"", "['");
You need \\ to escape in java regex and [ is a special character in java regex, thus the \\ in front of it. " is a special character in strings so you only need one \ to escape it.

"Test[\"".replaceAll("\\[\"", "['"); // Test['

Java Regular Expression Issue

The following exception is thrown when this [0-9]+_[0-9]+_[0-9]+(_[0-9]+){0,1} regex is used.
Caused by: java.util.regex.PatternSyntaxException: Unclosed counted closure near index 31
[0-9]+_[0-9]+_[0-9]+(_[0-9]+){0
^
at java.util.regex.Pattern.error(Pattern.java:1713)
at java.util.regex.Pattern.closure(Pattern.java:2759)
at java.util.regex.Pattern.group0(Pattern.java:2537)
at java.util.regex.Pattern.sequence(Pattern.java:1806)
at java.util.regex.Pattern.expr(Pattern.java:1752)
at java.util.regex.Pattern.compile(Pattern.java:1460)
at java.util.regex.Pattern.<init>(Pattern.java:1133)
at java.util.regex.Pattern.compile(Pattern.java:823)
I am reading this from a XML File.

You probably want this:
[0-9]+_[0-9]+_[0-9]+(_[0-9]+)?

You have to escape commas with backslash:
[0-9]+_[0-9]+_[0-9]+(_[0-9]+){0\,1}

Error reading log file with reg expression

I am trying to read a log file with the content look like this:
127.0.0.1 - - [17/OCT/2009:00:02:14 0000] GET xxxxxx xxxx xxx
I tried the following reg exp and I am getting ERROR: Unclosed group near index 90
regex = (\d+\.\d+\.\d+\.\d+)\s-\s-\s\[(\d+)/(\w{3})/(\d{4}):(\d{2}):(\d{2}):(\d{2})\s(\d{4}\)].*
Can someone help me?

You forgot escaping some chars:
^(\d+\.\d+\.\d+\.\d+)\s-\s-\s\[(\d+)\/(\w{3})\/(\d{4}):(\d{2}):(\d{2}):(\d{2})\s(\d{4})\]

I think the "[" and "]" should be escaped: [[] and []] or \[ and \].
For Java:
java.util.regex.Pattern.compile("(\\d+.\\d+.\\d+.\\d+)\\s-\\s-\\s\\[(\\d+)/(\\w{3})/(\\d{4}):(\\d{2}):(\\d{2}):(\\d{2})\\s(\\d{4})\\].*")

First, escape [ and ] with backslahes. They have special meaning in regexps.

[ and ] are special characters. That's what it means by unclosed group. Depending on your flavor of regex, you'll need to put either 1 \ or 2 \ in front of each bracket.
regex = (\d+.\d+.\d+.\d+)\s-\s-\s[(\d+)/(\w{3})/(\d{4}):(\d{2}):(\d{2}):(\d{2})\s(\d{4})].*

^\d+\.\d+\.\d+\.\d+\s-\s-\s\[\d{2}\/[A-Z]{3}\/\d{4}:\d{2}:\d{2}:\d{2}\s\d{4}]\sGET\s(.{6}\s.{4}\s.{3})$