How to use 'matches()' method to see if string matches format

Question

I'm currently working on something where the code inputs about thousands of lines of strings. Each line must follow a specific format like the following:

"Name,#,#,#,#,#,#"

Where 'name' is the name of a movie (we can assume the name won't have any numbers), and # is any number from 0-10. Each value MUST be separated by a comma.

My code is the following:

if (line.matches(".*[a-zA-z].*,([0-9]|10),([0-9]|10),([0-9]|10),([0-9]|10),([0-9]|10),([0-9]|10)")) {
       System.out.println("no");
}

else {
    System.out.println(line);

The issue is that the title of the film can't have commas in it. If it does, it needs to be printed. However, my 'matches()' doesn't seem to pick up lines that have a comma in the title. It seems to me that my code specifically outlines that if the next entry (separated by a comma) is not an integer, then it does not match, and therefore the 'line' needs to be printed.

Can anyone see where I'm going wrong in this?

Answer 1

You are saying that rules are:

• Lines must be 7 comma-separated values: a name and 6 numbers in range 0-10.
• The name must not contain a comma.
• We can assume the name won't have any numbers, but it is not a requirement that it cannot.

Since the only invalid character in a name is a comma, so regex would be:

[^,]*,(?:[0-9]|10),(?:[0-9]|10),(?:[0-9]|10),(?:[0-9]|10),(?:[0-9]|10),(?:[0-9]|10)

If you want to capture the fields, you would use this code:

Pattern p = Pattern.compile("([^,]*),([0-9]|10),([0-9]|10),([0-9]|10),([0-9]|10),([0-9]|10),([0-9]|10)");
for (String line : lines) {
    Matcher m = p.matcher(line);
    if (! m.matches()) {
        System.out.println("Invalid line: " + line);
    } else {
        System.out.println("Name: " + m.group(1));
        System.out.println("  Values: " + m.group(2)
                                  + " " + m.group(3)
                                  + " " + m.group(4)
                                  + " " + m.group(5)
                                  + " " + m.group(6)
                                  + " " + m.group(7));
    }
}

Test

String[] lines = { "Buffalo Bill and the Indians, or Sitting Bull's History Lesson,0,1,2,3,4,5",
                   "Dr. Strangelove or: How I Learned to Stop Worrying and Love the Bomb,6,7,8,9,10,0",
                   "300,1,2,3,4,5,6"};

Output

Invalid line: Buffalo Bill and the Indians, or Sitting Bull's History Lesson,0,1,2,3,4,5
Name: Dr. Strangelove or: How I Learned to Stop Worrying and Love the Bomb
  Values: 6 7 8 9 10 0
Name: 300
  Values: 1 2 3 4 5 6

First movie name has a comma, so it doesn't match.
Second movie name has special characters (. and :), but no comma, so it matches.
Third movie name is "300", which is an actual movie, so it matches.

Answer 2

The problem lies within with the .*. This part is able to include the comma.

Fri,dayaervsere,6,4,78,7
<--><--------->^
.*  [a-zA-Z]   ,(  [...]

So, basically you only need to get rid of the .*. Instead, apply a quantifier to your first group:

[a-zA-Z]* // to match any number of characters

or

[a-zA-Z]+ // to match at least one character

Answer 3

If you do use regex to solve this, I'd recommend allowing commas in the 'Name' part of your regex. Focus on making sure there are 6 numbers, each following a comma. You can check to see if the name fits an appropriate criteria later.

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


// before your for-loop, create a pattern (Assuming no digits in title)
Pattern p = Pattern.compile("([^0-9]+),([0-9]|10),([0-9]|10),([0-9]|10),([0-9]|10),([0-9]|10),([0-9]|10)");

// ...
// later on in your actual for-loop for each line.
Matcher m = p.matcher(line);

if (m.matches())
{
    String title = m.group(1);
    // do extra checking for the title if needed
}
else
{
    // print no
}

Answer 4

The following regex supposed to solve your problem:

^([a-zA-Z ]+),([0-9]|10),([0-9]|10),([0-9]|10),([0-9]|10),([0-9]|10),([0-9]|10)

Or the shorter version of it, with no code duplication:

^([a-zA-Z ]+)(,([0-9]|10)){6}

Testing

"The Killer,6,7,3,6,8,1" matches the pattern.

"The Kill,er,6,7,3,6,8,1" doesn't match the pattern, as you wanted.

Also, spaces in the title are supported.

You can play with it here.