Java regex

Think the problem is the ?.  It is probably being evaluated as a regex operator versus the literal string you want it to be.  I will see if I can remember how to escape.  You can try \? but think have to use character code.

Also, the ^ in the beginning says match on everything except the pattern you have set.

Think you want the opposite.

Take a look here for reference:
http://java.sun.com/j2se/1.4.2/docs/api/java/util/regex/Pattern.html

Also in your string, you have ?000 and you are trying to match with ?ooo.  Note that one is zeros (0) and other are letter o (O)

My bad! The String pattern should be  "KLDKFVN FDFJDVmmmm.nnn?ooo=9876ERFVS";
I tried regex = "^mmmm.nnnn?ooo=[0-9]+$" but didn't work.
I also tried to use \ as an escape character i.e. String regex = "^mmmm.nnnn\?ooo=[0-9]+?", I got syntax error :(

also tried regex = "^mmmm.nnnn\\(?\\)ooo=[0-9]+$", doesn't work :(

Think the statement needs an overhaul.  Just haven't figured out right pattern yet myself to offer you something different.  I would say take a look at the listing from the url I sent and start over from scratch.

^ == except, so don't think this will work in your case

public static void main(String[] args) {
 
    String regex = "mmmm.nnnn\\?ooo=[0-9]+";
    String replacement = "AAA mmmm.nnn?ooo=45302 EEEEEE FFFFF GGGGGG";
    String pattern =  "KLDKFVN FDFJDVmmmm.nnn?ooo=9876ERFVS";
 
    Pattern p = Pattern.compile(regex);
    Matcher m = p.matcher(pattern);
    if (m.find()) {
        pattern = m.group();
    }
    System.out.println(pattern);     // output ---> mmmm.nnn?ooo=9876          
}

I got the correct output for my first question. The regex = "mmmm.nnnn\\?ooo=[0-9]+" yields mmmm.nnn?ooo=9876. Now, how can we do the replacement?

Try this:

public static void main(String[] args) {
        
        String regex = "mmmm.nnn\\?ooo=[0-9]+"; 
        String replacement = "AAA mmmm.nnn?ooo=45302 EEEEEE FFFFF GGGGGG";
        String pattern =  "KLDKFVN FDFJDVmmmm.nnn?ooo=9876ERFVS";
     
        Pattern p = Pattern.compile(regex); 
        Matcher m = p.matcher(pattern);
        if (m.find()) {
            pattern = m.replaceAll(replacement);
        }
        System.out.println(pattern);     // output ---> mmmm.nnn?ooo=9876           
    }

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This will replace the whole thing:
 String regex = "^[^0-9]+mmmm.nnn\\?ooo=[0-9]+[^0-9]+$";

And it took me a while to realize, ^ does mean beginning of file as well as except, so see what you were trying to do. ;) Sorry!

If you wanted to get block starting with mmmm, then leave off the ^.  If you want all of it, you have to put in [^0-9]+ to tell the regex that there will be 1 or more non-digits in front of mmmm to start the string.

I double checked your solution non of them can generate a correct output. I don't know where did I get wrong!

import java.util.regex.Matcher;
import java.util.regex.Pattern;
 
public class TryRegex {
public static void main(String[] args) {
                
        String regex = "mmmm.nnn\\?ooo=[0-9]+"; 
        String replacement = "AAA mmmm.nnn?ooo=45302 EEEEEE FFFFF GGGGGG";
        String pattern =  "KLDKFVN FDFJDVmmmm.nnn?ooo=9876ERFVS";
     
        Pattern p = Pattern.compile(regex); 
        Matcher m = p.matcher(pattern);
        if (m.find()) {
            pattern = m.replaceAll(replacement);
        }
        System.out.println(pattern);     // output ---> mmmm.nnn?ooo=9876           
    }
}
The output of this one is "KLDKFVN FDFJDVAAA mmmm.nnn?ooo=45302 EEEEEE FFFFF GGGGGGERFVS"
-------------------------------------------------------------------
import java.util.regex.Matcher;
import java.util.regex.Pattern;
 
public class TryRegex  {
public static void main(String[] args) {
                
	String regex = "^[^0-9]+mmmm.nnn\\?ooo=[0-9]+[^0-9]+$";
        String replacement = "AAA mmmm.nnn?ooo=45302 EEEEEE FFFFF GGGGGG";
        String pattern =  "KLDKFVN FDFJDVmmmm.nnn?ooo=9876ERFVS";
     
        Pattern p = Pattern.compile(regex); 
        Matcher m = p.matcher(pattern);
        if (m.find()) {
            pattern = m.replaceAll(replacement);
        }
        System.out.println(pattern);     // output ---> mmmm.nnn?ooo=9876           
    }
}
The output of this one is "AAA mmmm.nnn?ooo=45302 EEEEEE FFFFF GGGGGG"
The correct output should be "AAA mmmm.nnn?ooo=9876 EEEEEE FFFFF GGGGGG" :(

Select allOpen in new window

I had tested all of them and replacement worked for me. I will see what you just posted though.  Just figured I would tell you that worked before I posted. ;)

Ah, well if the correct output shoudl be 9876 instead of 45302 why do you have that in the replacement string?

Well, replacement and pattern are two different strings.

String replacement = "AAA mmmm.nnn?ooo=45302 EEEEEE FFFFF GGGGGG";
String pattern =  "KLDKFVN FDFJDVmmmm.nnn?ooo=9876ERFVS";

However, they both have a similar pattern which is mmmm.nnn?ooo equal to a number. My question is asking how to get the number (9876) from the string pattern and replace the number (45302) of the string replacement i.e. to change the string replacement number (45302)  to 9876. Then the new string should be AAA mmmm.nnn?ooo=9876 EEEEEE FFFFF GGGGGG.

The regex = "mmmm.nnn\\?ooo=[0-9]+" can get the first step right to yield mmmm.nnn?ooo=9876 from the string pattern. The next step is we need to do substitution. How can we replace the mmmm.nnn?ooo=45302 from the string replacement with mmmm.nnn?ooo=9876 in order to have a new string AAA mmmm.nnn?ooo=9876 EEEEEE FFFFF GGGGGG.

Hope my question is more clear for you :)

Please see another solution (also provided by Guru mwvisa1) at https://www.experts-exchange.com/questions/23868976/Java-regex.html. Thanks a lot!!!