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Expression to capture only 1 occurrence for a single character but multiple for others

I am trying to use the following regex to capture following values. This is for use in Java.
(\$|£|$|£)([ 0-9.]+)
Example values which I do want to be captured via above regex which works.
$100
$100.5
$100
$100.6
£200
£200.6
But the following as gets captured which is wrong. I only want to capture values when thereis only 1 dot in the text. Not multiples.
£200.15.
£200.6.6.6.6
Is there a way to select such that multiple periods doesn't count?
I can't do something like following cos that would affect the numbers too. Please advice.
(\$|£|$|£)([ 0-9.]{1})

You can use
(\$|£|$|£)(\d+(?:\.\d+)?)\b(?!\.)
See the regex demo.
In this regex, (\d+(?:\.\d+)?)\b(?!\.) matches
(\d+(?:\.\d+)?) - Group 1: one or more digits, then an optional occurrence of . and one or more digits
\b - a word boundary
(?!\.) - not immediately followed with a . char.
Another solution for Java (where the regex engine supports possessive quantifiers) will be
(\$|£|$|£)(\d++(?:\.\d+)?+)(?!\.)
See this regex demo. \d++ and (?:\.\d+)?+ contain ++ and ?+ possessive quantifiers that prevent backtracking into the quantified subpatterns.
In Java, do not forget to double the backslashes in the string literals:
String regex = "(\\$|£|$|£)(\\d++(?:\\.\\d+)?+)(?!\\.)";

You could try this
(\$|£|$|£)([0-9]+(?:\.[0-9]+)?)$
one or more digits followed by an optional dot and some digits and then the end of the string.
EDIT: some typos fixed
And it's not ok to delete the whole sentence obove, due to one word against my self. :(

Problem coming up with appropriate Regex expression

I need to match text similar to the following text in an if statement.
REG#John Smith#14102245862#7 johns road new york#John Anthony Smith
The expression is meant to match a REG keyword at the beginning of the string then username followed by an account number composed of numbers with no specific restriction on the number of digits, then the address and lastly the name of the individual the address is registered to.
The Regex expression I had come up with is not working. The regex expression is below:
^REG\#\w\#[0-9]\#\w\#\w
May you kindly assist in showing me where I went wrong and how to make it work.
Thank you in advance

The problem is that you don't use quantifiers (* or +) and space is not included within \w which stands for [A-Za-z0-9_]. The character # does not need to be escaped (at least as far as I know in Java). Try the following Regex:
^REG#[\w ]+#\d+#[\w ]+#[\w ]+
^REG matches the beginning of the string (REG) literally
# matches self literally
[\w ]+ stands for at least one word character or space
\d+ stands for at least one digit
In Java, don't forget the double escaping:
String regex = "^REG#[\\w ]+#\\d+#[\\w ]+#[\\w ]+";

Try ^REG\#.*?\#[0-9]*?\#.*?\#.* , the operator *? means repeat until next slice of expression, in that case, \#

Regex + sign followed by numbers

Hi i want to find Strings like "+19" in Java
so a + sign followed by infinite amount of numbers.
How do i do this?
Tried "+[0123456789]"
and "\+[0123456789]"
thank you :)

This is the regex you want to use:
\\+\\d+
Two kinds of plus are being used here. The first is escaped with two backslashes because it is treated as a literal. The second one means match 1 of more times (i.e. match any digit one or more times).
Code:
String input = "+19";
if (input.matches("\\+\\d+")) {
System.out.println("input string matches");
}

Yes, to match a plus you need to escape it with two backslashes in a C string literal that Java uses. A literal plus needs to be either escaped or put into a character class, [+]. If you just use a plus symbol, it becomes a quantifier that matches the previous symbol or group one or more number of times.
Also, note that the \d shorthand digit class can match more than just ASCII digits if Pattern.UNICODE_CHARACTER_CLASS flag is passed to Pattern.compile (or embedded (?U) flag is added at the start of the pattern). It is advised to use unambiguous patterns in case the code might be maintained or enhanced/adjusted by different developers later.
Most people prefer patterns without escaping backslashes if possible since that allows to avoid issues like the one you faced.
Here is a version of the regex that does not require any escaping:
"[+][0-9]+"
Also, the plus quantifier does not match an infinite number of digits, only MAX_UINT number of times.

Need regular expression for pattern this

I need a regular expression for below pattern
It can start with / or number
It can only contain numbers, no text
Numbers can have space in between them.
It can contain /*, at least 1 number and space or numbers and /*
Valid Strings:
3232////33 43/323//
3232////3343/323//
/3232////343/323//
Invalid Strings:
/sas/3232/////dsds/
/ /34343///// /////
///////////
My Problem is, it can have space between numbers like /3232 323/ but not / /.
How to validate it ?
I have tried so far:
(\\d[\\d ]*/+) , (/*\\d[\\d ]*/+) , (/*)(\\d*)(/*)

This regex should work for you:
^/*(?:\\d(?: \\d)*/*)+$
Live Demo: http://www.rubular.com/r/pUOYFwV8SQ

My solution is not so simple but it works
^(((\d[\d ]*\d)|\d)|/)*((\d[\d ]*\d)|\d)(((\d[\d ]*\d)|\d)|/)*$

Just use lookarounds for the last criteria.
^(?=.*?\\d)([\\d/]*(?:/ ?(?!/)|\\d ?))+$
The best would have been to use conditional regex, but I think Java doesn't support them.
Explanation:
Basically, numbers or slashes, followed by one number and a space, or one slash and a space which is not followed by another slash. Repeat that. The space is made optional because I assume there's none at the end of your string.

Try this java regex
/*(\\d[\\d ]*(?<=\\d)/+)+
It meets all your criteria.
Although you didn't specifically state it, I have assumed that a space may not appear as the first or last character for a number (ie spaces must be between numbers)

"(?![A-z])(?=.*[0-9].*)(?!.*/ /.*)[0-9/ ]{2,}(?![A-z])"
this will match what you want but keep in mind it will also match this
/3232///// from /sas/3232/////dsds/
this is because part of the invalid string is correct
if you reading line by line then match the ^ $ and if you are reading an entire block of text then search for \r\n around the regex above to match each new line

Problem in regex for decimal number

I want a regex for decimal numbers like 00.0
I tried this [0-9]{1,2}(.[0-9]{1})? which works perfectly.
But I have to add ^ at begining and *$ at end.
Is there any way to have the regex work as the one working along with adding these characters?
^([0-9]{1,2}(.[0-9]{1})?)*$ --> fails to do what I want.
My regex should look like ^[Anything here]*$
Any help would be appreciated.
Thanks

Depends on the type of regex, but for many regex types (posix, posix extended, perl, python, emacs) . (dot) means match any symbol. To match the dot symbol you need to quote it like \..
And to match exactly one digit you don't need to add {1} at the end of it. I.e. [0-9]{1} is the same as [0-9].

I think you need .* at the end
but could you reply with some examples of strings you want to match and ones you don't want to match>

If I understand well what you need, have a try with :
\^\d\d?(\.\d)?\*\$
This will match
\^ a carret ^
\d\d? 1 or 2 digit
(\.\d)? eventually a dot and a digit
\* an asterisk
\$ a dollar

I figured out the problem was * and it could be excluded by adding a pair of parenthesis before * like ()*
And ^([0-9]{1,2}(\.[0-9])?)()*$ works well.