Pattern CANON_EQ field in Java with examples

The CANON_EQ field of the Pattern class matches two characters only if they are canonically equal. When you use this as flag value to the compile() method, two characters will be matched if and only if their full canonical decompositions are equal.

Where canonical decomposition is one of the Unicode text normalization forms.

Example 1

import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class CANON_EQ_Example {
   public static void main( String args[] ) {
      String regex = "b\u0307";
      //Compiling the regular expression
      Pattern pattern = Pattern.compile(regex, Pattern.CANON_EQ);
      //Retrieving the matcher object
      Matcher matcher = pattern.matcher("\u1E03");
      if(matcher.matches()) {
         System.out.println("Match found");
      } else {
         System.out.println("Match not found");
      }
   }
}

Output

Match found 

Example 2

import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class CANON_EQ_Example {
   public static void main( String args[] ) {
      String regex = "a\u030A";
      //Compiling the regular expression
      Pattern pattern = Pattern.compile(regex, Pattern.CANON_EQ);
      //Retrieving the matcher object
      String [] input = {"\u00E5", "a\u0311", "a\u0325", "a\u030A", "a\u1E03", "a\uFB03" };
      for (String ele : input) {
         Matcher matcher = pattern.matcher(ele);
         if(matcher.matches()) {
            System.out.println(ele+" is a match for "+regex);
         } else {
            System.out.println(ele+" is not a match for "+regex);
         }
      }
   }
}

Output

? is a match for a?
a? is not a match for a?
a? is not a match for a?
a? is a match for a?
a? is not a match for a?
a? is not a match for a?

Maruthi Krishna

Updated on: 06-Dec-2023

733 Views

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