How to do text processing in java

Question

I have a csv file

 input.csv
    1,[103.85,1.28992],[103.89,1.294],[103.83,1.216]
    2,[103.5,1.292],[103.9,1.4],[103.3,1.21]
    3,[103.6,1.291],[103.6,1.39],[103.3,1.29]

From this I need to convert it into

{

                    "type": "LineString",
                    "coordinates": [[103.85,1.28992],[103.89,1.294],[103.83,1.216]]


                "properties": {
                    "id": "1"

                }
            },
            {

                "type": "LineString",
                "properties": {
                    "id": "2"

                },
                "coordinates": [[103.5,1.292],[103.9,1.4],[103.3,1.21]]



        },{

                "type": "LineString",
                "properties": {
                    "id": "3"

                },
                "coordinates": [[103.6,1.291],[103.6,1.39],[103.3,1.29]]



        }

I am now trying to do it in java.So I read the csv file with open csv

try (CSVReader reader = new CSVReader(new FileReader(fileName))) {
            String[] nextLine;

            while ((nextLine = reader.readNext()) != null) {

                for (String e: nextLine) {
                   // System.out.format("%s ", e);
                System.out.println( e.split(",",1));
                }
            }

But I am having problem while spliting the line.If you look at the first line then I want to have 1 as a part and the rest [103.85,1.28992],[103.89,1.294],[103.83,1.216] as another part.So that I can build the String

  String s="{\"type\": \"LineString\", \"coordinates\": "+s[1]+"
     \"properties\": { \"id\":"+s[0]+"} }";

Any help is appreciated

@Jens i do not read a json file I read a csv and write a JSON file — user7477092
– user7477092, Commented Mar 6, 2017 at 8:14

Mustofa Rizwan · Accepted Answer · 2017-03-06 08:06:53Z

1

You can try that:

(\d+),(.*)

You don't need to split... if you execute it you get two group . Group 1 is the digit and Group 2 is the later contents Explanation

Try this Sample:

final String regex = "(\\d+),(.*)";
final String string = "1,[103.85,1.28992],[103.89,1.294],[103.83,1.216]\n"
     + "2,[103.5,1.292],[103.9,1.4],[103.3,1.21]\n"
     + "3,[103.6,1.291],[103.6,1.39],[103.3,1.29]";

final Pattern pattern = Pattern.compile(regex, Pattern.MULTILINE);
final Matcher matcher = pattern.matcher(string);

while (matcher.find()) {
    System.out.println(matcher.group(1));
    System.out.println(matcher.group(2));
}

edited Mar 6, 2017 at 8:06

answered Mar 6, 2017 at 8:03

Mustofa Rizwan

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2 Comments

user7477092 Over a year ago

Is this the parameter to split spilit.("(\d+),(.*)")?

user7477092 Over a year ago

Thank you for the explanation as well :)

gvlachakis · Accepted Answer · 2017-03-06 08:06:38Z

0

Use JSONSimple to create the JSON you need. IN my opinion the simplest JSON lib. See this example of use.

answered Mar 6, 2017 at 8:06

gvlachakis

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Comments

Maurice Perry · Accepted Answer · 2017-03-06 08:14:04Z

0

You can parse the lines yourself:

try (BufferedReader reader = new BufferedReader(new FileReader(fileName))) {
    String nextLine;
    while ((nextLine = reader.readLine()) != null) {
        int ix = nextLine.indexOf(',');
        if (ix >= 0) {
            String head = nextLine.substring(0, ix);
            String tail = nextLine.substring(ix+1);
            doSomethingWith(head, tail);
        }
    }
}

answered Mar 6, 2017 at 8:14

Maurice Perry

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2 Comments

user7477092 Over a year ago

Cannot invoke indexOf(char) on the array type String[] error throws for this

Maurice Perry Over a year ago

@Josh it's a String, not a String[]

Scott Conway · Accepted Answer · 2017-05-08 20:46:01Z

0

The problem is that to get the data the way you need to have whatever is generating the input.csv file to encapsulate the different sections in quotes.

So either

input.csv
   1,"[103.85,1.28992],[103.89,1.294],[103.83,1.216]"
   2,"[103.5,1.292],[103.9,1.4],[103.3,1.21]"
   3,"[103.6,1.291],[103.6,1.39],[103.3,1.29]"

Or

input.csv
   "1","[103.85,1.28992],[103.89,1.294],[103.83,1.216]"
   "2","[103.5,1.292],[103.9,1.4],[103.3,1.21]"
   "3","[103.6,1.291],[103.6,1.39],[103.3,1.29]"

Because as it is between the one and the end of the line there are six commas which any csv parser will interpret that the line has seven columns instead of two.

answered May 8, 2017 at 20:46

Scott Conway

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