In java, how can I read data from file and create a collection of arrays?

Question

I am trying to run Junit Parameterized test. Following is how Junit suggests to add data to collection of arrays.

Object[][] data = new Object[][] { { 1 }, { 2 }, { 3 }, { 4 } };  
return Arrays.asList(data);

This however requires user to add the data in the code. I want to read data from file (about 300 lines) and convert it into collection of Arrays. How can I do that ?

Here is the code:

import static org.junit.Assert.*;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.junit.runners.Parameterized;
import org.junit.runners.Parameterized.Parameters;



@RunWith(value=Parameterized.class)
public class UrlParameterizedTest {

    private String url;
    public static ArrayList<String>dataArray=new ArrayList<String>();
    static File directory = new File(".");
    public static String fileToRead;

    public UrlParameterizedTest(String url){
        this.url=url;
    }
    @Parameters
    public static Collection<Object[]> data() throws Exception {

        try {
            fileToRead=directory.getCanonicalPath()+"\\Data\\LinkChecker.csv";
            loadDataFile(fileToRead);
        } catch (IOException e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
        }

    Object[][]data=new Object[dataArray.size()][];
      *******   //convert dataArray to data here.************
        return Arrays.asList(data);

    }

    @Test
    public void testURLs() {
        System.out.println("Parameterized Number is "+url);
    }

    public static void loadDataFile(String dataFile) throws Exception {
        dataArray.clear();
        //if data_file is absolute, use this
        try
        {
            // Open an input stream
            // Read a line of text
            String line="";
            BufferedReader br=new BufferedReader(new FileReader(dataFile));
            while((line=br.readLine())!=null) {
                dataArray.add(line);
            }
            br.close();
            System.out.println("The data file length is "+ dataArray.size());
        }

        catch (IOException e)
        {
            e.printStackTrace();
            System.out.println ("Unable to read from file");
        }
    }
}

@TechExchange : I guess OP wants to read inputs( 1,2,3,4 ) from file — Bhavik Shah
– Bhavik Shah, Commented Jan 31, 2013 at 11:43
@TechExchange: My questions is based on blogs.oracle.com/jacobc/entry/…. As Bhavik pointed out, I want to read {1},{2},{3},{4} from a CSV file. According to the above mentioned ref., Parameter's data method must return a collection of Arrays. Now, I already have a method that reads data from csv and puts that into an arrayList. I want to convert that arrayList into Object[][]data. In short, 300 lines in csv file should result in 300 parameterized test methods. — Amit Chaudhari
– Amit Chaudhari, Commented Feb 1, 2013 at 1:49

John B · Accepted Answer · 2013-01-31 11:44:04Z

2

Use Apache Commons FileUtils.readFileToString to read the file to a string. Then you will need to parse the file into the collection of arrays. We cannot help you on how to parse the file and we don't know the contents.

FileUtils.readFileToString

answered Jan 31, 2013 at 11:44

John B

33.1k8 gold badges80 silver badges100 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Amit Chaudhari Over a year ago

@Bhavik: List is a good option. How to turn that list into a collection of arrays ?

John B Over a year ago

That depends on your file. You need to parse or group the lines into arrays. We don't know if each line is a comma-separated list of values or if you are going to combine a set of lines into an array or if each line is a single entry in the array. You have to figure SOME of these things out for yourself.

Cisco · Accepted Answer · 2013-01-31 11:59:06Z

In order to retrieve strings from a File you could use something like the follow code; then you could retrieve data from your ArrayList and put them in your array (using "toArray()" method provided by Class ArrayList).

ArrayList<String> strings=new ArrayList<String >();
String filePath = path + "/" + fileName;

FileInputStream fin = null;
            try {
                fin = new FileInputStream(filePath);
            } catch (IOException e) {
                System.out.println (e.toString()); 
                System.out.println("File " + fileName + " not found.");
            }

            DataInputStream in = new DataInputStream(fin);
            BufferedReader br = new BufferedReader(new InputStreamReader(in));
            String strLine = null;


            while ((strLine = br.readLine()) != null)   {

                strings.add(strLine);
            }

            in.close();

bane · Accepted Answer · 2013-01-31 12:11:03Z

0

Put your data in a file, one under the other. Use a scanner to read them as strings and then convert them to numbers (I assumed that they should be float numbers). Something like this:

ArrayList<Float> numbers = new ArrayList<Float>();
Scanner scanner = new Scanner(file);
while(scanner.hasNextLine()) {
    String nextLine = scanner.nextLine();
    float value = Float.parseFloat(nextLine);
    numbers.add(value);
}
scanner.close();

edited Jan 31, 2013 at 12:11

bane

8411 gold badge9 silver badges23 bronze badges

answered Jan 31, 2013 at 11:51

missrg

5852 gold badges8 silver badges19 bronze badges

Collectives™ on Stack Overflow

In java, how can I read data from file and create a collection of arrays?

3 Answers 3

2 Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

2 Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related