Java Queries Here..

[TheSloth]

There is also project Euler. Also look forward to Advent of Code every year.

Hey man! Do you still participate in these?

 

[TheSloth]

Need help in understanding why reg ex pattern

((/?)([A-Z]{3})([0-9]{1,15}))

is returning false for input

ABC123/DEF1223456/GHI12345678980834

Sample code:

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class RegExCHGSTagPattern {
  public static void main(String[] args) {
  String input1 = "ABC123";
  String input2 = "ABC123/DEF1223456/GHI12345678980834";
  Pattern p = Pattern.compile("((/?)([A-Z]{3})([0-9]{1,15}))");
  Matcher m1 = p.matcher(input1);
  Matcher m2 = p.matcher(input2);
  System.out.println("output1-"+m1.matches());
  while(m2.find()) {
    System.out.println(m2.group()+"-"+p.matcher(m2.group()).matches());
  }
  System.out.println("output2-"+m2.matches());
  }
}

@Desmond @khalil1210 @quicky008

 

[Desmond]

I think you haven't escaped the first forward slash.

I matched all the groups in your string using this regex:

([A-Z]{3}\d{1,15})\/?

Edit: Replaced \d+ with \d{1,15} since you have a constraint on the number of digits.

 

[TheSloth]

I think you haven't escaped the first forward slash.

I matched all the groups in your string using this regex:

([A-Z]{3}\d{1,15})\/?

Edit: Replaced \d+ with \d{1,15} since you have a constraint on the number of digits.

I am trying but its not working in IDE. i did match the strings on *regex101.com/

View attachment 1724080208719.png

 

[khalil1210]

Try with this website to test with different inputs which can come up - *regex101.com/r/4dq5xR/1

Pattern p = Pattern.compile("([A-Z]{1,3}[0-9]{1,15}/?)+");

I think this code should work

Explanation for my code --
[A-Z]{1,3} --> any character from A to Z which will repeat for minimum 1 to maximum 3 times
[0-9]{1,15} --> any number from 0 to 9 which will repeat for minimum 1 to maximum 15 times
/? --> / can come for zero or more times

this regex can possibly match with strings like [A-Z]{1,3}[0-9]{1,15}/? -->
ABC123
DEF123/
X1
YZ23/
XYZ123456789012345/

But we want the above group to come one or more times, so we can mention it as group and add + for one or more times

final regex is - ([A-Z]{1,3}[0-9]{1,15}/?)+

View attachment 1724081351825.png

 

[TheSloth]

The problem is I am able to match the regex with online compiler. But for some reason it's not working in IDE. I am using Java 17

 

[Desmond]

I am trying but its not working in IDE. i did match the strings on *regex101.com/

View attachment 22926

In Java you have to escape the backslashes for regex Strings.

private static final String pattern = "([A-Z]{3}\\d{1,15})\\/?";

class Main {

    private static final String pattern = "([A-Z]{3}\\d{1,15})\\/?";
 
    private static final String input = "ABC123/DEF1223456/GHI12345678980834";
 
    public static void main(String[] args) {
        Pattern p = Pattern.compile(pattern);
        Matcher m = p.matcher(input);
        while(m.find()) {
            System.out.println(m.group(1));
        }
    }
}

Yields:

ABC123
DEF1223456
GHI12345678980834

With some group adjustment, the ending slashes can be excluded.

Edit: Apparently, simply using group(1) will match the bracketed group in the regex. Updated the answer to reflect that.

 

[Desmond]

BTW, note that regex implementations are not standard and different languages/platforms have slightly different behaviour.

 

[TheSloth]

In Java you have to escape the backslashes for regex Strings.

private static final String pattern = "([A-Z]{3}\\d{1,15})\\/?";

class Main {

    private static final String pattern = "([A-Z]{3}\\d{1,15})\\/?";
 
    private static final String input = "ABC123/DEF1223456/GHI12345678980834";
 
    public static void main(String[] args) {
        Pattern p = Pattern.compile(pattern);
        Matcher m = p.matcher(input);
        while(m.find()) {
            System.out.println(m.group(1));
        }
    }
}

Yields:

ABC123
DEF1223456
GHI12345678980834

With some group adjustment, the ending slashes can be excluded.

Edit: Apparently, simply using group(1) will match the bracketed group in the regex. Updated the answer to reflect that.

if you add m.matches() line at the end, it returns false. This is exactly my question, we are able to see the group from the entire input which matches, I am wondering why m.matches() return false at the end.

 

[TheSloth]

Try with this website to test with different inputs which can come up - *regex101.com/r/4dq5xR/1

Pattern p = Pattern.compile("([A-Z]{1,3}[0-9]{1,15}/?)+");

I think this code should work

Explanation for my code --
[A-Z]{1,3} --> any character from A to Z which will repeat for minimum 1 to maximum 3 times
[0-9]{1,15} --> any number from 0 to 9 which will repeat for minimum 1 to maximum 15 times
/? --> / can come for zero or more times

this regex can possibly match with strings like [A-Z]{1,3}[0-9]{1,15}/? -->
ABC123
DEF123/
X1
YZ23/
XYZ123456789012345/

But we want the above group to come one or more times, so we can mention it as group and add + for one or more times

final regex is - ([A-Z]{1,3}[0-9]{1,15}/?)+

View attachment 22927

It worked! Adding the + symbol at the end of the entire group returns true. You are a saviour <3

 

[Desmond]

Ok, I misunderstood your question. I thought you wanted to extract the individual components of the string.

Though I would use \d instead of [0-9] since it matches single digits, while the [] notation works if you are creating an alphanumeric pattern.