Why am i getting NullPointerException in this class?

Error:

Exception in thread "main" java.lang.NullPointerException

at wine.DataSet.getDataSetSize(DataSet.java:37)

at wine.DataSet.(DataSet.java:16)

at wine.main.main(main.java:9)

C:\Users\Denis\AppData\Local\NetBeans\Cache\8.2\executor-snippets un.xml:53: Java returned: 1

BUILD FAILED (total time: 0 seconds)

Code:

package wine;

import java.io.File; import java.io.FileNotFoundException; import java.util.Scanner;

public final class DataSet {

private DataSample[] dataArray; public int samples; public String[] sampleArr; public int label; public DataSet(String filename)throws FileNotFoundException{ System.out.println("Calculating number of lines..."); getDataSetSize(filename); DataSample[] dataArray = new DataSample[samples]; double[] attributes=new double[samples]; //to convert string array into doubles array

for(int i=0;i

for(int j=1;j

dataArray[i]=new DataSample(label,attributes); } System.out.println(dataArray[0]); } public int getDataSetSize(String filename) throws FileNotFoundException { samples=0; File file = new File(filename); try (Scanner input = new Scanner(file)) { while (input.hasNextLine()){ sampleArr[samples]=input.nextLine(); //sampleArr , has each line read from file samples++; } input.close(); System.out.println("done "); } return samples; } public double[] getMean(int label){ double x[] = null; return x; } public double[] getStd(int label){ return null; } public DataSample[] getDataSet(){ return dataArray; } }

main:

package wine;

import java.io.FileNotFoundException; import java.util.Arrays;

public class main { public static void main(String[] args) throws FileNotFoundException { DataSet train = new DataSet("wine.txt"); System.out.println(train.samples); } }