Parsing using Pattern in Java

Question

I want to Parse the lines of a file Using parsingMethod

test.csv

 Frank George,Henry,Mary / New York,123456
,Beta Charli,"Delta,Delta Echo
", 25/11/1964, 15/12/1964,"40,000,000.00",0.0975,2,"King, Lincoln ",Alpha

This is the way i read line

 public static void main(String[] args) throws Exception {


        File file = new File("C:\\Users\\test.csv");
        BufferedReader reader = new BufferedReader(new FileReader(file));   
        String line2;
        while ((line2= reader.readLine()) !=null) {
            String[] tab = parsingMethod(line2, ",");
            for (String i : tab) {
                System.out.println( i );
            }
        }


    }

    public static String[] parsingMethod(String line,String parser) {

        List<String> liste = new LinkedList<String>();
        String patternString ="(([^\"][^"+parser+ "]*)|\"([^\"]*)\")" +parser+"?";
        Pattern pattern = Pattern.compile(patternString);
        Matcher matcher =pattern.matcher(line);

        while (matcher.find()) {
            if(matcher.group(2) != null){
                liste.add(matcher.group(2).replace("\n","").trim());
            }else if(matcher.group(3) != null){
                liste.add(matcher.group(3).replace("\n","").trim());
            }       
        }

        String[] result = new String[liste.size()];
        return liste.toArray(result);
    }
}

Output :

Frank George
Henry
Mary / New York
123456

Beta Charli
Delta
Delta Echo
"
25/11/1964
15/12/1964
40,000,000.00
0.0975
2
King
Lincoln
"
Alpha
Delta
Delta Echo

I want to remove this " , Can any one help me to improve my Pattern.

Expected output

Frank George
Henry
Mary / New York
123456
Beta Charli
Delta
Delta Echo
25/11/1964
15/12/1964
40,000,000.00
0.0975
2
King
Lincoln
Alpha
Delta
Delta Echo

Output for line 3

25/11/1964
15/12/1964

40
000
000.00


0.0975
2

King
Lincoln

How does this compile? you are assigning an array of strigns to patternString. String patternString = "(([^\"][^","]*)|\"([^\"]*)\")","?"; — Joan
– Joan, Commented May 15, 2013 at 8:54
This code not compile, you have an error on: String patternString = "(([^\"][^","]*)|\"([^\"]*)\")","?"; — Ricardo Cacheira
– Ricardo Cacheira, Commented May 15, 2013 at 9:09
@Joan : I am not good in pattern String. But this code compiles. I copied the output from console. — GameBuilder
– GameBuilder, Commented May 15, 2013 at 9:41
@RicardoCacheira : I am not good in pattern String. But this code compiles. I copied the output from console — GameBuilder
– GameBuilder, Commented May 15, 2013 at 9:42
As anana says, you must scape the double backslashes, but even if you do that, the program will not return an output. I tryied. — Joan
– Joan, Commented May 15, 2013 at 9:50

CloudyMarble · Accepted Answer · 2013-05-15 10:11:29Z

2

Your code didn't compile properly but that was caused by some of the " not being escaped.

But this should do the trick:

String patternString = "(?:^.,|)([^\"]*?|\".*?\")(?:,|$)";
Pattern pattern = Pattern.compile(patternString, Pattern.MULTILINE);

(?:^.,|) is a non capturing group that matches a single character at the start of the line

([^\"]*?|\".*?\") is a capturing group that either matches everything but " OR anything in between " "

(?:,|$) is a non capturing group that matches a end of the line or a comma.

Note: ^ and $ only work as stated when the pattern is compiled with the Pattern.MULTILINE flag

edited May 15, 2013 at 10:11

CloudyMarble

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answered May 15, 2013 at 9:55

B8vrede

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6 Comments

GameBuilder Over a year ago

I am not in Patterns. Now i have corrected my code()see question. I put your PatternString in my code. It gives me Error ` java.lang.IndexOutOfBoundsException: No group 2`

B8vrede Over a year ago

This pattern returns it one group at the time so there is no group 2. To check if there is a group to check out matcher.groupCount()

B8vrede Over a year ago

And if you really want to have multiple group use this: String patternString = "(?:(?:^.,|)([^\"]*?|\".*?\")(?:,|$))+"; (I didn't test this one but i should work)

GameBuilder Over a year ago

@B8rede : Not working same erroe java.lang.IndexOutOfBoundsException: No group 2

B8vrede Over a year ago

Use

if(matcher.groupCount() >= 2){ 	            liste.add(matcher.group(2).replace("\n","").trim()); 	        }else if(matcher.groupCount() >= 3){ 	            liste.add(matcher.group(3).replace("\n","").trim()); 	        }

it will check if there is a group 2 and if it's there use it. Same for 3.

|

anana · Accepted Answer · 2013-05-15 11:16:44Z

1

I can't reproduce your result but I'm thinking maybe you want to leave the quotes out of the second captured group, like this:

"(([^\"][^"+parser+ "]*)|\"([^\"]*))\"" +parser+"?"

Edit: Sorry, this won't work. Maybe you want to let any number of ^\" in the first group as well, like this: (([^,\"]*)|\"([^\"]*)\"),?

edited May 15, 2013 at 11:16

answered May 15, 2013 at 9:16

anana

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6 Comments

anana Over a year ago

I'm sorry but I don't understand what you're saying. If my solution didn't work I'm sure someone else will bother to spoonfeed it to you.

GameBuilder Over a year ago

I request you to check my code. with the patternString in my code i cannot Parse " . I want to remove " also . And with your PatternString my Output is like , , ,000.00 ,

anana Over a year ago

The problem is I can't reproduce your result. Can you output line3 as it is passed to parserMethod? What if you change it to this (([^,\"]*)|\"([^\"]*)\"),? ?

anana Over a year ago

That makes no sense to me. Try to output line 3 so I can reproduce your results.

anana Over a year ago

I don't mean the output, but the input, the String that is given as an argument to parseMethod().

|

Ricardo Cacheira · Accepted Answer · 2013-05-15 12:20:25Z

1

As i can see the lines are related so try this:

    public static void main(String[] args) throws Exception {

        File file = new File("C:\\Users\\test.csv");
        BufferedReader reader = new BufferedReader(new FileReader(file));
        StringBuilder line = new StringBuilder();
        String lineRead;
        while ((lineRead = reader.readLine()) != null) {
            line.append(lineRead);
        }
        String[] tab = parsingMethod(line.toString());
        for (String i : tab) {
            System.out.println(i);
        }


    }

    public static String[] parsingMethod(String line) {

        List<String> liste = new LinkedList<String>();
        String patternString = "(([^\"][^,]*)|\"([^\"]*)\"),?";
        Pattern pattern = Pattern.compile(patternString);
        Matcher matcher = pattern.matcher(line);

        while (matcher.find()) {
            if (matcher.group(2) != null) {
                liste.add(matcher.group(2).replace("\n", "").trim());
            } else if (matcher.group(3) != null) {
                liste.add(matcher.group(3).replace("\n", "").trim());
            }
        }

        String[] result = new String[liste.size()];
        return liste.toArray(result);
    }

Ouput:

Frank George
Henry
Mary / New York
123456
Beta Charli
Delta,Delta Echo
25/11/1964
15/12/1964
40,000,000.00
0.0975
2
King, Lincoln
Alpha

as Delta, Delta Echo is in a quotation this should appear in the same line ! like as King, Lincoln

edited May 15, 2013 at 12:20

answered May 15, 2013 at 12:08

Ricardo Cacheira

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5 Comments

GameBuilder Over a year ago

Your PatternString and my PatternString is Same . this is a output only when you consider file content as a String. You have to read the file line by line and send it to parserMethod.

Ricardo Cacheira Over a year ago

Sorry mate but you told that the quotation mark on the beggining of line 3 id the close to the quotation started at line 2, so it tells me that the lines are related. If not you don't know what you want !!!

GameBuilder Over a year ago

Yes, the beginning of line 3 id the close to the quotation started at line 2. but it's line 3 and i have to parse each line separately.That is why I reading each line and parsing it using the method. Sorry for not being clear. Hope now you understand and will help me to solve this.

Ricardo Cacheira Over a year ago

It's not making sense to me, but ok ! Just to make sense, can you tell what is that lines and what you want to do? I'll try to help

Ricardo Cacheira Over a year ago

what have produced lines in test.csv ?

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