CODEWITHSUNDEEP
javaregexpattern-matching
Eduardo
Eduardo

Reputation: 45

Java Matcher not working

I have the function:

Boolean rhyme(String words) {
  Pattern pattern = Pattern.compile("...");
  Matcher matcher = pattern.matcher(words);
  matcher.matches();
  return matcher.group(1).equals(matcher.group(2));
}

where String words contains two words separated by a \t like: read\tdead. The function is supposed to check to see if the last three letters of each word are equal, and if so returns true, otherwise return false.

I can't change any of the code, I'm just supposed to create the regex expression so that this functions works.

My current expression is (.{3}?)(?=[\t])|(.{3}$) and when I plug this into regex101 it seems to work. When I use that expression in the function, I get an java.lang.IllegalStateException: No match found error. Can anyone help me figure out where I am going wrong, and remember, I can't change any of the code except for the pattern expression.

Upvotes: 0

Views: 179

Answers (1)

john16384
john16384

Reputation: 8044

The code is flawed unfortunately. More needs to be changed to make this work, because if there is no match (ie, words don't end with the same 3 letters) then matcher.matches() will return false. Continuing with the next statement will then always throw an exception as there was no match, and therefore there are no groups to access.

Working example (with tweaked regex):

boolean rhyme(String words) {
   Pattern pattern = Pattern.compile(".*(.{3})(?=[\\t]).*(.{3}$)");
   Matcher matcher = pattern.matcher(words);

   return matcher.matches() && matcher.group(1).equals(matcher.group(2));
}

Upvotes: 2

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