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Pattern COMMENTS field in Java with examples
The COMMENTS field of the Pattern class allows whitespace and comments in pattern. When you use this as flag value to the compile() method, white spaces and, comments starting with # are ignored in the given pattern.
Example 1
import java.util.Scanner;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class COMMENTES_Example {
public static void main( String args[] ) {
Scanner sc = new Scanner(System.in);
System.out.println("Enter input data: ");
String input = sc.nextLine();
//Regular expression to find digits
String regex = "\d #ignore this comment\n";
//Compiling the regular expression
Pattern pattern = Pattern.compile(regex, Pattern.COMMENTS);
//Retrieving the matcher object
Matcher matcher = pattern.matcher(input);
int count = 0;
String result = "";
while (matcher.find()) {
count++;
result = result+matcher.group();
}
System.out.println("Number of digits in the given text: "+count);
}
}Output
Enter input data: sample1 text2 with3 numbers4 in5 between6 Number of digits in the given text: 6
Example 2
import java.util.Scanner;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class COMMENTES_Example {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
System.out.println("Enter your name: ");
String name = sc.nextLine();
System.out.println("Enter your Date of birth: ");
String dob = sc.nextLine();
//Regular expression to accept date in MM-DD-YYY format
String regex = "^(1[0-2]|0[1-9])/
# For Month\n" + "(3[01]|[12][0-9]|0[1-9])/
# For Date\n" + "[0-9]{4}$ # For Year";
//Creating a Pattern object
Pattern pattern = Pattern.compile(regex, Pattern.COMMENTS);
//Creating a Matcher object
Matcher matcher = pattern.matcher(dob);
boolean result = matcher.matches();
if(result) {
System.out.println("Given date of birth is valid");
} else {
System.out.println("Given date of birth is not valid");
}
}
}Output
Enter your name: Krishna Enter your Date of birth: 09/26/1989 Given date of birth is valid
Updated on: 20-Nov-2019
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