org.sonar.l10n.java.rules.java.S5860.html Maven / Gradle / Ivy

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Why is this an issue?
Why use named groups only to never use any of them later on in the code?
This rule raises issues every time named groups are:

   defined but never called anywhere in the code through their name; 
   defined but called elsewhere in the code by their number instead; 
   referenced while not defined. 

Noncompliant code example
String date = "01/02";

Pattern datePattern = Pattern.compile("(?<month>[0-9]{2})/(?<year>[0-9]{2})");
Matcher dateMatcher = datePattern.matcher(date);

if (dateMatcher.matches()) {
  checkValidity(dateMatcher.group(1), dateMatcher.group(2));  // Noncompliant - numbers instead of names of groups are used
  checkValidity(dateMatcher.group("day")); // Noncompliant - there is no group called "day"
}

// ...

String score = "14:1";

Pattern scorePattern = Pattern.compile("(?<player1>[0-9]+):(?<player2>[0-9]+)"); // Noncompliant - named groups are never used
Matcher scoreMatcher = scorePattern.matcher(score);

if (scoreMatcher.matches()) {
  checkScore(score);
}

Compliant solution
String date = "01/02";

Pattern datePattern = Pattern.compile("(?<month>[0-9]{2})/(?<year>[0-9]{2})");
Matcher dateMatcher = datePattern.matcher(date);

if (dateMatcher.matches()) {
  checkValidity(dateMatcher.group("month"), dateMatcher.group("year"));
}

// ...

String score = "14:1";

Pattern scorePattern = Pattern.compile("(?<player1>[0-9]+):(?<player2>[0-9]+)");
Matcher scoreMatcher = scorePattern.matcher(score);

if (scoreMatcher.matches()) {
  checkScore(scoreMatcher.group("player1"));
  checkScore(scoreMatcher.group("player2"));
}

Or, using dedicated variables instead of group names:
String score = "14:1";

String player = "([0-9]+)";
String gameScore = player + ":" + player;

Pattern scorePattern = Pattern.compile(gameScore);
Matcher scoreMatcher = scorePattern.matcher(score);

if (scoreMatcher.matches()) {
  checkScore(score);
}