Regular expression is creating an empty array that should not exist

Question

I'm trying to parse a tab separated value dump from the IMDB. (The actual dump contains an inconsistent amount of tabs throughout each line.):

$, Claw         "OnCreativity" (2012)  [Himself]

$, Homo         Nykytaiteen museo (1986)  [Himself]  <25>
                   Suuri illusioni (1985)  [Guests]  <22>

$hutter         Battle of the Sexes (2017)  (as $hutter Boy)  [Bobby Riggs Fan]  <10>
                   NVTION: The Star Nation Rapumentary (2016)  (as $hutter Boy)  [Himself]  <1>
                   Secret in Their Eyes (2015)  (uncredited)  [2002 Dodger Fan]
                   Steve Jobs (2015)  (uncredited)  [1988 Opera House Patron]
                   Straight Outta Compton (2015)  (uncredited)  [Club Patron/Dopeman]

$lim, Bee Moe       Fatherhood 101 (2013)  (as Brandon Moore)  [Himself - President, Passages]
                   For Thy Love 2 (2009)  [Thug 1]
                   Night of the Jackals (2009) (V)  [Trooth]
                   "Idle Talk" (2013)  (as Brandon Moore)  [Himself]
                   "Idle Times" (2012) {(#1.1)}  (as Brandon Moore)  

$ly, Yung           Town Bizzness Pt 3 (2014) (V)  [Yung $ly]
                   "From Tha Bottom 2 Tha Top" (2016)  [Yung $ly]
                   "From Tha Bottom 2 Tha Top" (2016) {T-Pain (#1.2)}  [Yung $ly]

$torm, Cuntry       From the Woods: The Discovery of LYB (????)  (as Country $torm)  [Himself]

& Davi, Bruninho   Michel na Balada (2011) (V)  [Themselves]
                   Michel TelÛ: Sunset (2013) (V)  [Themselves]
                   "Programa da Sabrina" (2014) {(2016-01-23)}  [Themselves]

& Dollar Furado, Caio Corsalette    "Som Brasil" (2007) {ZezÈ di Camargo & Luciano (#5.7)}  [Themselves]

& Fabiano, CÈsar Menotti    Nascemos para Cantar (2010) (TV)  [Themselves]
                            Show da Virada (2011) (TV)  [Themselves - Performers]
                            Teleton 2010 (2010) (TV)  [Themselves]
                            "Altas Horas" (2000) {(2013-06-29)}  [Themselves]
                            "Altas Horas" (2000) {(2013-12-14)}  [Themselves]
                            "Eliana" (2009) {(2012-10-21)}  [Themselves]
                            "Tudo … PossÌvel" (2005) {(2008-04-13)}  [Themselves]
                            "TV Xuxa" (2005) {(2013-01-05)}  [Themselves]

My code:

package com.mycompany.imdbproject;

import java.io.BufferedReader;
import java.io.File;
import java.io.IOException;
import java.nio.charset.Charset;
import java.nio.file.Files;
import java.util.logging.Level;
import java.util.logging.Logger;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class ActorListParser {

Charset charset = Charset.forName("ISO-8859-1");

BufferedReader reader = null;

public ActorListParser() {

    try {

        this.reader = Files.newBufferedReader(
                new File(System.getProperty("user.home") + ("/IMDBLogs" + "/dataDirectory" + "/acsshort.txt")).toPath(), charset);

        String line = null;

        while ((line = reader.readLine()) != null) {
            String[] lineAsArray = null;

            Pattern startsWithTab = Pattern.compile("^\t.*$");

            Matcher tab = startsWithTab.matcher(line);

            boolean startsWithTabMatcher = tab.matches();

            if (!startsWithTabMatcher) {

                lineAsArray = line.split("\t");

                for (int i = 0;i < lineAsArray.length; i++) {

                    System.out.println("Length: " + lineAsArray.length +", Value:"+ i +"  "+ lineAsArray[i]);
                }
            }else{
            //parse lines that start with a tab (actor's other movies)
            }

        }
    } catch (IOException ex) {

        Logger.getLogger(ActorListParser.class.getName()).log(Level.SEVERE, null, ex);

    }
}

public static void main(String[] args) {
    ActorListParser acp = new ActorListParser();
}

}

The output:

Length: 2, Value:0  $, Claw
Length: 2, Value:1          "OnCreativity" (2012)  [Himself]
Length: 1, Value:0  
Length: 2, Value:0  $, Homo
Length: 2, Value:1          Nykytaiteen museo (1986)  [Himself]  <25>
Length: 1, Value:0    
Length: 2, Value:0  $hutter
Length: 2, Value:1          Battle of the Sexes (2017)  (as $hutter Boy)  [Bobby Riggs Fan]  <10>
Length: 1, Value:0  
Length: 2, Value:0  $lim, Bee Moe
Length: 2, Value:1      Fatherhood 101 (2013)  (as Brandon Moore)  [Himself - President, Passages]
Length: 1, Value:0  
Length: 2, Value:0  $ly, Yung
Length: 2, Value:1      Town Bizzness Pt 3 (2014) (V)  [Yung $ly]
Length: 1, Value:0  
Length: 2, Value:0  $torm, Cuntry
Length: 2, Value:1      From the Woods: The Discovery of LYB (????)  (as Country $torm)  [Himself]
Length: 1, Value:0  
Length: 2, Value:0  & Davi, Bruninho
Length: 2, Value:1  Michel na Balada (2011) (V)  [Themselves]
Length: 1, Value:0  
Length: 2, Value:0  & Dollar Furado, Caio Corsalette
Length: 2, Value:1  "Som Brasil" (2007) {ZezÃ di Camargo & Luciano (#5.7)}  [Themselves]
Length: 1, Value:0  
Length: 2, Value:0  & Fabiano, CÃsar Menotti
Length: 2, Value:1  Nascemos para Cantar (2010) (TV)  [Themselves]

As you can see, I take the first appearance of the author's name and parse the name and movie from it.(for later use in a Map). I will get the other movies attributed to the actor in a separate regex.

Unfortunately, there is an array of length 1 with no value that keeps appearing in my output. What am I doing incorrectly that is creating this empty array?

Two tabs in a row would generate that empty value, maybe split on \t+ ? — Maarten Bodewes
– Maarten Bodewes, Commented Jul 20, 2016 at 22:14
What do you think the return value of "".split("\t") is? Hint: It's an array of one value: An empty string. See javadoc: If the expression does not match any part of the input then the resulting array has just one element, namely this string. — Andreas
– Andreas, Commented Jul 20, 2016 at 22:18
Any reason not to use one of the many excellent open source CSV parsing libraries? — dnault
– dnault, Commented Jul 20, 2016 at 22:19

janos · Accepted Answer · 2016-07-20 22:29:05Z

4

You have empty lines in the input. These don't start with a tab character, so they match the if statement. Then, splitting an empty line on anything will result in an array of length 1 with an empty string element. For example, "".split("blah") returns an array of length 1 with an empty string element in it. That's just the way String.split works.

So, the solution is to add a check for !line.isEmpty().

@Andreas said it best in a comment:

Yup. See javadoc: If the expression does not match any part of the input then the resulting array has just one element, namely this string.

edited Jul 20, 2016 at 22:29

answered Jul 20, 2016 at 22:20

janos

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4 Comments

Andreas Over a year ago

Yup. See javadoc: If the expression does not match any part of the input then the resulting array has just one element, namely this string.

user465001 Over a year ago

@janos. That's it. Thank you. I can't accept your answer until 3 minutes has passed. I really goofed that.

Wiktor Stribiżew Over a year ago

Or !line.trim().isEmpty().

user465001 Over a year ago

Thank you Andreas and Wiktor.

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