Develop Reference

RegEx for matching between any two HTML tags

I have the following content :
<div class="TEST-TEXT">hi</span>
first young CEO's TEST-TEXT
<span class="test">hello</span>
I am trying to match the TEST-TEXT string to replace it is value but only when it is a text and not within an attribute value.
I have checked the concepts of look-ahead and look-behind in Regex but the current issue with that is that it needs to use a fixed width for the match here is a link regex-match-all-characters-between-two-html-tags that show case a very similar case but with an exception that there is a span with a class to create a match
also checked the link regex-match-attribute-in-a-html-code
here are two regular expressions I am trying with :
\"([^"]*)\"
(?s)(?<=<([^{]*)>)(.+?)(?=</.>)
both are not working for me try using [https://regex101.com/r/ApbUEW/2]
I expect it to match only the string when it is a text
current behavior it matches both cases
Edit : I want the text to be dynamic and not specific to TEST-TEXT

Something like this should help:
\>([^"<]*)\<
EDIT:
Without open and close tags included:
(?<=\>)([^"<]*)(?=\<)

Try TEST-TEXT(?=<\/a>)
TEST-TEXT matches TEST-TEXT
?= look ahead to check closing tag </a>
see at
regex101

Here, we might just add a soft boundary on the right of the desired output, which you have been already doing, then a char list for the desired output, then collect, after that we can make a replacement by using capturing groups (). Maybe similar to this:
([A-Z-]+)(<\/)
Demo
This snippet is just to show that the expression might be valid:
const regex = /([A-Z-]+)(<\/)/gm;
const str = `<div class="TEST-TEXT">hi</span><a href=\\"https://en.wikipedia.org/wiki/TEST-TEXT\\">first young CEO's
TEST-TEXT</a><span class="test">hello</span><div class="TEST-TEXT">hi</span><a href=\\"https://en.wikipedia.org/wiki/TEST-TEXT\\">first young CEO's
TEST-TEXT</a><span class="test">hello</span>`;
const subst = `NEW-TEXT$2`;
// The substituted value will be contained in the result variable
const result = str.replace(regex, subst);
console.log('Substitution result: ', result);
RegEx
If this expression wasn't desired, it can be modified or changed in regex101.com.
RegEx Circuit
jex.im also helps to visualize the expressions.

Maybe this will help?
String html = "<div class=\"TEST-TEXT\">hi</span>\n" +
"first young CEO's TEST-TEXT\n" +
"<span class=\"test\">hello</span>";
Pattern pattern = Pattern.compile("(<)(.*)(>)(.*)(TEST-TEXT)(.*)</.*>");
Matcher matcher = pattern.matcher(html);
while (matcher.find()){
System.out.println(matcher.group(5));
}

A RegEx for that a string between any two HTML tags
(?![^<>]*>)(TEST\-TEXT)

How to get the middle strings with regex?

I have an input string that looks like this
DatalogSetupFile: BTS50xx1EJA\3.20\log_all.stp
The DatalogSetupFile: and \3.20\log_all.stp are constant. I wish to extract BTS50xx1EJA from the string. How should I do it?

You can make a regex group in which you can specify what all are the static content and then specify what are the dynamic content as a whole group, So that you can get the dynamic content as a whole group,
You can define regex as follow
^(?:DatalogSetupFile:\s)(.*)(?:\3.20\log_all.stp)$
Try this Demo
Here you can use the first group to get your dynamic string

Give this regex a try:
\s\K[^\\]+
Which, in Java would look like:
String myInputString = "DatalogSetupFile: BTS50xx1EJA\\3.20\\log_all.stp";
Pattern myPattern = Pattern.compile("\\s\\K[^\\\\]+");
Matcher myMatcher = Pattern.matcher(myInputString);
System.out.println(myMatcher.group(0));

Find the google loginform with java pattern

I am trying to search the google loginform within the html code with a simple java pattern. The loginform looks like this:
<form ... id="gaia_loginform" ... > ... </form>
I am using the following pattern to find it:
Pattern pat = Pattern.compile("<form[^>]*id=[\"|']gaia_loginform[\"|'][^>]*>(.*)</form>")
Matcher mat = pat.find(html); // html is the complete website
System.out.println(mat.group(1)); // throws exception
Actually it should the contents between the two tags. Thanks for advice what I am doing wrong :)

You are misusing the Matcher. Here is how it should be used (an example of using the Matcher):
String str = "<form ... id=\"gaia_loginform\" ... >\nCONTENT\n</form>";
Pattern pat = Pattern.compile("<form\\b[^>]*\\bid=[\"']gaia_loginform[\"'][^>]*>(.*?)</form>", Pattern.DOTALL);
Matcher matcher = pat.matcher(str);
while (matcher.find()) {
System.out.println(matcher.group(1));
}
See IDEONE demo
For parsing HTML you should consider using HTML parsers, even if you are not using them now.
A couple of words on the regex: I am using Pattern.DOTALL flag when declaring the regex as . should be able to match newline symbols. Tag and id names must be matches as whole words and thus I am using \\b. Instead of .* we are safer with .*? (lazy matching), it will capture as few characters as possible.

Negating a Regular Expression for string replacement

I have the following code that can replace the email address in a String in Java:
addressStr.replaceFirst("([a-zA-Z0-9_\\-\\.]+)#((\\[[0-9]{1,3}\\.[0-9]{1,3}\\.[0-9]{1,3}\\.)|(([a-zA-Z0-9\\-]+\\.)+))([a-zA-Z]{2,4}|[0-9]{1,3})", "")
So, a string with John Smith <john#smith.com> would become John Smith <>. How do I negate it so that it will instead replace all that doesn't match the email address and have the final result as just john#smith.com?
I tried to put in the ^ and ?<= at the front but it doesn't work.

Well, it's not the regex you need to change but the calling code. Your regex matches the e-mail address (in a weird way), and the replace() removes it from the string.
So just use
Pattern regex = Pattern.compile("([a-zA-Z0-9_\\-\\.]+)#((\\[[0-9]{1,3}\\.[0-9]{1,3}\\.[0-9]{1,3}\\.)|(([a-zA-Z0-9\\-]+\\.)+))([a-zA-Z]{2,4}|[0-9]{1,3})");
Matcher regexMatcher = regex.matcher(addressStr);
if (regexMatcher.find()) {
address = regexMatcher.group();
}

The complete Java regex for catching e-mails would be as follows:
"(?:[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*|\"(?:[\\x01-\\x08\\x0b\\x0c\\x0e-\\x1f\\x21\\x23-\\x5b\\x5d-\\x7f]|\\\\[\\x01-\\x09\\x0b\\x0c\\x0e-\\x7f])*\")#(?:(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?|\\[(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?|[a-z0-9-]*[a-z0-9]:(?:[\\x01-\\x08\\x0b\\x0c\\x0e-\\x1f\\x21-\\x5a\\x53-\\x7f]|\\\\[\\x01-\\x09\\x0b\\x0c\\x0e-\\x7f])+)\\])"
Take a look at https://www.rfc-editor.org/rfc/rfc2822#section-3.4.1 for more info on this.
A bit complicated but it is valid for all known and valid emails formats (yours do not allows mails like bob+bib#gmail.com which are valid).
For your problem, as stated multiple times, just find (stealing Tim Pietzcker piece of code):
Pattern regex = Pattern.compile("(?:[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*|\"(?:[\\x01-\\x08\\x0b\\x0c\\x0e-\\x1f\\x21\\x23-\\x5b\\x5d-\\x7f]|\\\\[\\x01-\\x09\\x0b\\x0c\\x0e-\\x7f])*\")#(?:(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?|\\[(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?|[a-z0-9-]*[a-z0-9]:(?:[\\x01-\\x08\\x0b\\x0c\\x0e-\\x1f\\x21-\\x5a\\x53-\\x7f]|\\\\[\\x01-\\x09\\x0b\\x0c\\x0e-\\x7f])+)\\])");
Matcher regexMatcher = regex.matcher(addressStr);
foundMatch = regexMatcher.find();

You can try:
String mailId = Pattern.compile(regexp, Pattern.LITERAL).matcher(addressStr).group();
Idea here is to get the matched string rather than trying to replace everything else with blank. You can extract the pattern into a field if this operation is repetitive.

Just don't replace.... use match(es) instead.

Java regular expression for extracting the data between tags

I am trying to a regular expression which extracs the data from a string like
<B Att="text">Test</B><C>Test1</C>
The extracted output needs to be Test and Test1. This is what I have done till now:
public class HelloWorld {
public static void main(String[] args)
{
String s = "<B>Test</B>";
String reg = "<.*?>(.*)<\\/.*?>";
Pattern p = Pattern.compile(reg);
Matcher m = p.matcher(s);
while(m.find())
{
String s1 = m.group();
System.out.println(s1);
}
}
}
But this is producing the result <B>Test</B>. Can anybody point out what I am doing wrong?

Three problems:
Your test string is incorrect.
You need a non-greedy modifier in the group.
You need to specify which group you want (group 1).
Try this:
String s = "<B Att=\"text\">Test</B><C>Test1</C>"; // <-- Fix 1
String reg = "<.*?>(.*?)</.*?>"; // <-- Fix 2
// ...
String s1 = m.group(1); // <-- Fix 3
You also don't need to escape a forward slash, so I removed that.
See it running on ideone.
(Also, don't use regular expressions to parse HTML - use an HTML parser.)

If u are using eclipse there is nice plugin that will help you check your regular expression without writing any class to check it.
Here is link:
http://regex-util.sourceforge.net/update/
You will need to show view by choosing Window -> Show View -> Other, and than Regex Util
I hope it will help you fighting with regular expressions

It almost looks like you're trying to use regex on XML and/or HTML. I'd suggest not using regex and instead creating a parser or lexer to handle this type of arrangement.

I think the bestway to handle and get value of XML nodes is just treating it as an XML.
If you really want to stick to regex try:
<B[^>]*>(.+?)</B\s*>
understanding that you will get always the value of B tag.
Or if you want the value of any tag you will be using something like:
<.*?>(.*?)</.*?>