//From an example in Big Java, by Cay Horstman
import java.io.*;
import java.util.*;
public class DataSetReader
{
   //Instance Variable: stores data from input file
	private double[] data;
	
   //"Opens" the named file to make it available for reading
   //Creates a Scanner to interpret the text file
	public double[] readFile(String fileName) throws IOException
	{
		FileReader reader = new FileReader(fileName);
		Scanner scan = new Scanner(reader);
		try
		{
			readData(scan);
		}
		finally
		{
			reader.close();
		}
		return this.data;
	}
	
   //Instantiate an array to store the input data
   //Coordinates input and storing of the data
	private void readData(Scanner scan)
	{
		if  ( !scan.hasNextInt() )
			throw new DataException("Integer count expected");
			
		int dataCount = scan.nextInt();
		
		this.data = new double[dataCount];
		
		for (int index = 0; index < dataCount; index++)
			readItem(scan, index);
			
		if  ( scan.hasNext() )
			throw new DataException("End of file expected");
	}
	
   //Inputs the next data item from the file
   // and stores it into the data array
	private void readItem(Scanner scan, int index)
	{
		if ( !scan.hasNext() )
			throw new DataException("Another data item expected");
			
		if ( !scan.hasNextDouble() )
			throw new DataException("Double value expected. Found > " + scan.next() + " < instead");

		double item = scan.nextDouble();
		data[index] = item;
	}
}