Question

Please use the Java program below to test the following regex pattern (in the table) and record the output, and explain how the output is generated.

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

public class RegexTestBarness {
  
       public static void main(String[] arg) {
              Scanner input = new Scanner(System.in);
                while (true) {
                   System.out.println("Enter a regex pattern: ");
                   String regex = input.nextLine();
                  
                   // Create a regex pattern
                    Pattern pt = Pattern.compile(regex);
                  
                    System.out.println("Enter a input string to search: ");
                    String sr = input.nextLine();
                  
                    // Create a Matcher object
                    Matcher mt = pt.matcher(sr);

                    boolean found = false;
                    while (mt.find()) {
                        System.out.printf("I found the text \"%s\" starting at " +
                                          "index %d and ending at index %d.\n",
                                          mt.group(), mt.start(), mt.end());
                      
                        found = true;
                    }
                  
                    if(!found){
                        System.out.println("No match found.");
                    }
                }
       }
}

regex pattern	test string	output	explanation
[^abc]	abc	No match found.	Any character except a, b, or c
GAATTC	TGCAGAATTCGGG
\d	Homework01
\D	2010
\s	this is a regex
\s+	this is a   regex
[A-Z][A-Z]\s\d{5}	MD 20943

Answer 1

regex pattern	test string	output	explanation
[^abc]	abc	No match found.	Any character except a, b, or c
GAATTC	TGCAGAATTCGGG	I found the text "GAATTC" starting at index 4 and ending at index 10.	Find the substring in String
\d	Homework01	I found the text "0" starting at index 8 and ending at index 9. I found the text "1" starting at index 9 and ending at index 10.	Find for the integer
\D	2010	No match found.	Matches the nondigits
\s	this is a regex	I found the text " " starting at index 4 and ending at index 5. I found the text " " starting at index 7 and ending at index 8. I found the text " " starting at index 9 and ending at index 10.	Matches the whitespace
\s+	this is a   regex	I found the text " " starting at index 4 and ending at index 5. I found the text " " starting at index 7 and ending at index 8. I found the text " " starting at index 9 and ending at index 12.	matches the one or more spaces
[A-Z][A-Z]\s\d{5}	MD 20943	I found the text "MD 20943" starting at index 0 and ending at index 8.	Match Two any Character in capital followed by space and followed by 5 digit integer

/*****************************RegexTestBarness.java************************/

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

public class RegexTestBarness {

   public static void main(String[] arg) {
       Scanner input = new Scanner(System.in);
       while (true) {
           System.out.println("Enter a regex pattern: ");
           String regex = input.nextLine();

           // Create a regex pattern
           Pattern pt = Pattern.compile(regex);

           System.out.println("Enter a input string to search: ");
           String sr = input.nextLine();

           // Create a Matcher object
           Matcher mt = pt.matcher(sr);

           boolean found = false;
           while (mt.find()) {
               System.out.printf("I found the text \"%s\" starting at " + "index %d and ending at index %d.\n",
                       mt.group(), mt.start(), mt.end());

               found = true;
           }

           if (!found) {
               System.out.println("No match found.");
           }
       }
   }
}
/********************output**********************/

Please let me know if you have any doubt or modify the answer, Thanks:)