Java Regular Expressions and Dollar Sign

Java regular expressions and dollar sign

You need to escape $ in the regex with a back-slash (\), but as a back-slash is an escape character in strings you need to escape the back-slash itself.

You will need to escape any special regex char the same way, for example with ".".

String pattern = "/feedback/com\\.navteq\\.lcms\\.common\\.domain\\.poi\\.feedback\\.Review\\$0(.)*";

Java regex (java.util.regex). Search for dollar sign

You may use

String search = "/bla/$V_N.$XYZ.bla";
String pattern = "[%$]([^%.$]*)";
Matcher matcher = Pattern.compile(pattern).matcher(search);
while (matcher.find()){
    System.out.println(matcher.group(1)); 
} // => V_N, XYZ

See the Java demo and the regex demo.

NOTE

• You do not need an optional \1? at the end of the pattern. As it is optional, it does not restrict match context and is redundant (as the negated character class cannot already match neither $ nor%)
• [%$]([^%.$]*) matches % or $, then captures into Group 1 any zero or more
  chars other than %, . and $. You only need Group 1 value, hence, matcher.group(1) is used.
• In a character class, neither . nor $ are special, thus, they do not need escaping in [%.$] or [%$].

New line and dollar sign in Java regular expression

Your regex does not match the input string. In fact, $ matches the end of string (at the end of line3). Since you are not using an s flag, the . cannot get there.

NOTE! that the $ anchor - even without Pattern.MULTILINE option - can match a position before the final line feed char, see What is the difference between ^ and \A , $ and \Z in regex?. This can be easily tested with "a\nb\n".replaceAll("$", "X"), resulting in "a\nbX\nX", see this Java demo.

More, the $ end of line/string anchor cannot have ? quantifier after it. It makes no sense for the regex engine, and is ignored in Java.

To make it work at all, you need to use s flag if you want to just return http://www.google.com:

String test_domain = "http://www.google.com/path\nline2\nline3";
test_domain = test_domain.replaceFirst("(?s)(\\.[^:/]+).*$", "$1");
System.out.println(test_domain);

Output of this demo:

http://www.google.com

With a multiline (?m) flag, the regex will process each line looking for a literal . and then a sequence of characters other than : and /. When one of these characters is found, the rest of characters on that line will be omitted.

    String test_domain = "http://www.google.com/path\nline2\nline3";
    test_domain = test_domain.replaceFirst("(?m)(\\.[^:/]+).*$", "$1");
    System.out.println(test_domain);

Output of this IDEONE demo:

http://www.google.com
line2
line3

How do you escape dollar and braces, (i.e. ${title}) in a java regular expression?

Not sure how the last one would result in an error; it'd just not match anything because you're using too many backslashes on the $.

This should work:

string.replaceAll("\\$\\{title\\}", title);

How to get a dollar sign in Java regex

Here is a 2-step approach: we extract <...> groups with a regex and then split the chunks into words and see if they start with $.

String s = "<$FB $TWTR are getting plummetted>";
Pattern pattern = Pattern.compile("<([^>]+)>");
Matcher matcher = pattern.matcher(s);
while (matcher.find()){
    String[] chks = matcher.group(1).split(" ");
    for (int i = 0; i<chks.length; i++)
    {
        if (chks[i].startsWith("$"))
            System.out.println(chks[i].substring(1));
    }
} 

See demo

And here is a 1-regex approach (see demo), use only if you feel confident with regex:

String s = "<$FB $TWTR are getting plummetted>";
Pattern pattern = Pattern.compile("(?:<|(?!^)\\G)[^>]*?\\$([A-Z]+)");
Matcher matcher = pattern.matcher(s);
while (matcher.find()){
    System.out.println(matcher.group(1)); 
} 

The regex used here is (?:<|(?!^)\G)[^>]*?\$([A-Z]+).

It matches:

• (?:<|(?!^)\G) - A literal < and then at the end of each successful match
• [^>]*? - 0 or more characters other than > (as few as possible)
• \$ - literal $
• ([A-Z]+) - match and capture uppercase letters (replace with what best suits your purpose, perhaps \\w).

Java Regular Expression to match dollar amounts

Since you're doing this to learn regex...

^\$(([1-9]\d{0,2}(,\d{3})*)|(([1-9]\d*)?\d))(\.\d\d)?$

Breakdown:

^\$ start of string with $ a single dollar sign

([1-9]\d{0,2}(,\d{3})*) 1-3 digits where the first digit is not a 0, followed by 0 or more occurrences of a comma with 3 digits

or

(([1-9]\d*)?\d) 1 or more digits where the first digit can be 0 only if it's the only digit

(\.\d\d)?$ with a period and 2 digits optionally at the end of the string

Matches:

$4,098.09
$4098.09
$0.35
$0
$380

Does not match:

$098.09
$0.9
$10,98.09
$10,980456

String#replaceAll() method not replacing for $ (dollar)

String.replaceAll is for regular expressions. '$' is a special character in regular expressions.

If you are not trying to use regular expressions, use String.replace, NOT String.replaceAll.

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