I have a string like the following:
SYBASE_OCS=OCS-12_5
SYBASE=/opt/sybase/oc12.5.1-EBF12850
//there is a newline here as well
The string at the debugger appears like this:
I am trying to match the part coming after SYBASE=, meaning I'm trying to match /opt/sybase/oc12.5.1-EBF12850.
To do that, I've written the following code:
String key = "SYBASE";
Pattern extractorPattern = Pattern.compile("^" + key + "=(.+)$");
Matcher matcher = extractorPattern.matcher(variableDefinition);
if (matcher.find()) {
return matcher.group(1);
}
The problem I'm having is that this string on 2 lines is not matched by my regex, even if the same regex seems to work fine on regex 101.
State of my tests:
If I don't have multiple lines (e.g. if I only had SYBASE=... followed by the new line), it would match
If I evaluate the expression extractorPattern.matcher("SYBASE_OCS=OCS-12_5\\nSYBASE=/opt/sybase/oc12.5.1-EBF12850\\n") (note the double backslash in front of the new line), it would match.
I have tried to use variableDefinition.replace("\n", "\\n") to what I give to the matcher(), but it doesn't match.
It seems something simple but I can't get out of it. Can anyone please help?
Note: the string in that format is returned by a shell command, I can't really change the way it gets returned.
The anchors ^ and $ anchors the match to the start and end of the input.
In your case you would like to match the start and end of a line within the input string. To do this you'll need to change the behavior of these anchors. This can be done by using the multi line flag.
Either by specifying it as an argument to Pattern.compile:
Pattern.compile("regex", Pattern.MULTILINE)
Or by using the embedded flag expression: (?m):
Pattern.compile("(?m)^" + key + "=(.+)$");
The reason it seemed to work in regex101.com is that they add both the global and multi line flag by default:
Does Java have a built-in way to escape arbitrary text so that it can be included in a regular expression? For example, if my users enter "$5", I'd like to match that exactly rather than a "5" after the end of input.
Since Java 1.5, yes:
Pattern.quote("$5");
Difference between Pattern.quote and Matcher.quoteReplacement was not clear to me before I saw following example
s.replaceFirst(Pattern.quote("text to replace"),
Matcher.quoteReplacement("replacement text"));
It may be too late to respond, but you can also use Pattern.LITERAL, which would ignore all special characters while formatting:
Pattern.compile(textToFormat, Pattern.LITERAL);
I think what you're after is \Q$5\E. Also see Pattern.quote(s) introduced in Java5.
See Pattern javadoc for details.
First off, if
you use replaceAll()
you DON'T use Matcher.quoteReplacement()
the text to be substituted in includes a $1
it won't put a 1 at the end. It will look at the search regex for the first matching group and sub THAT in. That's what $1, $2 or $3 means in the replacement text: matching groups from the search pattern.
I frequently plug long strings of text into .properties files, then generate email subjects and bodies from those. Indeed, this appears to be the default way to do i18n in Spring Framework. I put XML tags, as placeholders, into the strings and I use replaceAll() to replace the XML tags with the values at runtime.
I ran into an issue where a user input a dollars-and-cents figure, with a dollar sign. replaceAll() choked on it, with the following showing up in a stracktrace:
java.lang.IndexOutOfBoundsException: No group 3
at java.util.regex.Matcher.start(Matcher.java:374)
at java.util.regex.Matcher.appendReplacement(Matcher.java:748)
at java.util.regex.Matcher.replaceAll(Matcher.java:823)
at java.lang.String.replaceAll(String.java:2201)
In this case, the user had entered "$3" somewhere in their input and replaceAll() went looking in the search regex for the third matching group, didn't find one, and puked.
Given:
// "msg" is a string from a .properties file, containing "<userInput />" among other tags
// "userInput" is a String containing the user's input
replacing
msg = msg.replaceAll("<userInput \\/>", userInput);
with
msg = msg.replaceAll("<userInput \\/>", Matcher.quoteReplacement(userInput));
solved the problem. The user could put in any kind of characters, including dollar signs, without issue. It behaved exactly the way you would expect.
To have protected pattern you may replace all symbols with "\\\\", except digits and letters. And after that you can put in that protected pattern your special symbols to make this pattern working not like stupid quoted text, but really like a patten, but your own. Without user special symbols.
public class Test {
public static void main(String[] args) {
String str = "y z (111)";
String p1 = "x x (111)";
String p2 = ".* .* \\(111\\)";
p1 = escapeRE(p1);
p1 = p1.replace("x", ".*");
System.out.println( p1 + "-->" + str.matches(p1) );
//.*\ .*\ \(111\)-->true
System.out.println( p2 + "-->" + str.matches(p2) );
//.* .* \(111\)-->true
}
public static String escapeRE(String str) {
//Pattern escaper = Pattern.compile("([^a-zA-z0-9])");
//return escaper.matcher(str).replaceAll("\\\\$1");
return str.replaceAll("([^a-zA-Z0-9])", "\\\\$1");
}
}
Pattern.quote("blabla") works nicely.
The Pattern.quote() works nicely. It encloses the sentence with the characters "\Q" and "\E", and if it does escape "\Q" and "\E".
However, if you need to do a real regular expression escaping(or custom escaping), you can use this code:
String someText = "Some/s/wText*/,**";
System.out.println(someText.replaceAll("[-\\[\\]{}()*+?.,\\\\\\\\^$|#\\\\s]", "\\\\$0"));
This method returns: Some/\s/wText*/\,**
Code for example and tests:
String someText = "Some\\E/s/wText*/,**";
System.out.println("Pattern.quote: "+ Pattern.quote(someText));
System.out.println("Full escape: "+someText.replaceAll("[-\\[\\]{}()*+?.,\\\\\\\\^$|#\\\\s]", "\\\\$0"));
^(Negation) symbol is used to match something that is not in the character group.
This is the link to Regular Expressions
Here is the image info about negation:
I'm writing a utility to extract the names of header files from JSPs. I have no problem reading the JSPs line by line and finding the lines I need. I am having a problem extracting the specific text needed using regex. After looking at many similar questions I'm hitting a brick wall.
An example of the String I'll be matching from within is:
<jsp:include page="<%=Pages.getString(\"MY_HEADER\")%>" flush="true"></jsp:include>
All I need is MY_HEADER for this example. Any time I have this tag:
<%=Pages.getString
I need what comes between this:
<%=Pages.getString(\" and this: )%>
Here is what I have currently (which is not working, I might add) :
String currentLine;
while ((currentLine = fileReader.readLine()) != null)
{
Pattern pattern = Pattern.compile("<%=Pages\\.getString\\(\\\\\"([^\\\\]*)");
Matcher matcher = pattern.matcher(currentLine);
while(matcher.find()) {
System.out.println(matcher.group(1).toString());
}}
I need to be able to use the Java RegEx API and regex to extract those header names.
Any help on this issue is greatly appreciated. Thanks!
EDIT:
Resolved this issue, thankfully. The tricky part was, after being given the right regex, it had to be taken into account that the String I was feeding to the regex was always going to have two " / " characters ( (/"MY_HEADER"/) ) that needed to be escaped in the pattern.
Here is what worked (thanks to the help ;-)):
Pattern pattern = Pattern.compile("<%=Pages\\.getString\\(\\\\\"([^\\\\\"]*)");
This should do the trick:
<%=Pages\\.getString\\(\\\\\"([^\\\\]*)
Yeah that's a scary number of back slashes. matcher.group(1) should return MY_HEADER. It starts at the \" and matches everything until the next \ (which I assume here will be at \")%>.)
Of course, if your target text contains a backslash (\), this will not work. But you didn't give an indication that you'd ever be looking for something like <%=Pages.getString(\"Fun!\Yay!\")%> -- where this regex would only return Fun! and ignore the rest.
EDIT
The reason your test case was failing is because you were using this test string:
String currentLine = "<%=Pages.getString(\"MY_HEADER\")%>";
This is the equivalent of reading it in from a file and seeing:
<%=Pages.getString("MY_HEADER")%>
Note the lack of any \. You need to use this instead:
String sCurrentLine = "<%=Pages.getString(\\\"MY_HEADER\\\")%>";
Which is the equivalent of what you want.
This is test code that works:
String currentLine = "<%=Pages.getString(\\\"MY_HEADER\\\")%>";
Pattern pattern = Pattern.compile("<%=Pages\\.getString\\(\\\\\"([^\\\\]*)");
Matcher matcher = pattern.matcher(currentLine);
while(matcher.find()) {
System.out.println(matcher.group(1).toString());
}
Given a String that begin's with the symbols: {" and ends with: "}. There are other punctuation's present in between the line aswell, like: , ' or "" etc. How to use java regex utility to know whether the given String starts with: {". I am trying to return the Boolean value by using:
Pattern.matches(begin, string)
where
begin = "[\\p{Punct}&&[{]]"
and
string = {"name":"Aman"},{"surname":"Gupta"}.
(Please suggest regex option than JSON) I want to do it by using regex only. Please suggest a way how to achieve this.
You should try smth like this:
Pattern p = Pattern.compile("\{.*?\}");
Matcher m = p.matcher(/*your string here*/);
while (m.find()){
String substringInBraces = m.group();
/*do smth with your substring*/
}
This will give you a substring of anything that might be between two nearest curly braces.
You might be interested in reading this and this
Pattern.compile("^{").matcher(string).find()
I don't know why you insist on using \\p{Punct}, it's totally unnecessary here.
Note that Pattern.matches() wants to match the entire string, so it is not useful when you only want to match something at the start of a string.
I have one problem when i am using following code snippet
String regexString=regexPair.get(paramName);
Pattern p = Pattern.compile(regexString);
Matcher m = p.matcher(paramMap.get(paramName)[0]);
status = m.matches();
it return false
where regexPair is hashmap and regexPair.get(paramName) is
"^[_A-Za-z0-9-]+(\\.[_A-Za-z0-9-]+)*#[A-Za-z0-9]+(\\.[A-Za-z0-9]+)*(\\.[A-Za-z]{2,})$"
while I will ureplace
String regexString="^[_A-Za-z0-9-]+(\\.[_A-Za-z0-9-]+)*#[A-Za-z0-9]+(\\.[A-Za-z0-9]+)*(\\.[A-Za-z]{2,})$"
then it works fine
paramMap.get(paramName)[0] return agsd#gmail.com.
I am not getting why this is occurring please help me.
How do you know that regexPair.get(paramName) is the string you’ve given? Is that the result of some println call?
I suspect the quoting is not entirely the same. It may be that regexPair.get(paramName) actually contains '\\' followed by another '\\' (that is, two real backslashes in succession), while the replacement only contains "\\" (which is a single backslash). Note that the string "(\\." is really only 3 characters long.