CODEWITHSUNDEEP
javaif-statementnewline
user2533660
user2533660

Reputation: 151

If statement that is supposed to filter out newline not filtering new lines.

I'm writing a Regex pattern that filters through HTML tags and prints only the contents of valid tags for practice. While the pattern itself appears to be matching tags correctly, I am running into an issue when printing them. 

import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class HTMLPattern{
   public static void main(String[] args){

      Scanner in = new Scanner(System.in);
      int testCases = Integer.parseInt(in.nextLine());

      while(testCases>0){
          String line = in.nextLine();
          String tagPattern = "<([^>]+)>([^<]*?)</\\1>";
          Pattern p = Pattern.compile(tagPattern, Pattern.MULTILINE);
          Matcher m = p.matcher(line);
          if(m.find()){
              //checks if the output equals a newline
              if(m.group(2).matches("[\\n\\r]+")){
                   System.out.println("None");     
              }else{
                   System.out.println(m.group(2));
              }
          }else{
              System.out.println("None");
          }
         testCases--;
      }
   }
}

When inputting:

3
<a>test</a>
<b></b>
<c>test</c>

My output should be:

test
None
test

But instead it is:

test

test

My question is: Why is my if-statement not catching the newline and printing "None"?

Upvotes: 0

Views: 127

Answers (2)

user2533660
user2533660

Reputation: 151

Turns out there are no newline(s) present in the if statement. While my previous attempts for checking if(m.group(2) == null) failed, the .isEmpty() method correctly matched the null value I was testing for:

if(m.find()){
   if(m.group(2).isEmpty()){
      System.out.println("None");     
      }else{
         System.out.println(m.group(2));
      }
   }else{
      System.out.println("None");
   }

Upvotes: 0

Aleksandr Podkutin
Aleksandr Podkutin

Reputation: 2570

There is no new line, there is just empty string, try to match empty string like this:

if (m.group(2).matches("^$")) {

Or check length of string:

if (m.group(2).length() == 0) {

Upvotes: 2

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