将java程序转换为android程序时出错

Question

这是我的java程序中的java类

package stock_PKG;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.GregorianCalendar;
import java.net.URL;
import java.net.URLConnection;
import java.util.Scanner;

public class StockDownloader {
    public static final int DATE = 0;
    public static final int OPEN = 1;
    public static final int HIGH = 2;
    public static final int LOW = 3;
    public static final int CLOSE = 4;
    public static final int VOLUME = 5;
    public static final int ADJCLOSE = 6;

    private ArrayList <GregorianCalendar> dates;
    private ArrayList <Double> opens;
    private ArrayList <Double> highs;
    private ArrayList <Double> lows;
    private ArrayList <Double> closes;
    private ArrayList <Integer> volumes;
    private ArrayList <Double> adjCloses;

    public StockDownloader (String symbol, GregorianCalendar start, GregorianCalendar end)
    {
        dates = new ArrayList <GregorianCalendar> ();
        opens = new ArrayList <Double> ();
        highs = new ArrayList <Double> ();
        lows = new ArrayList <Double> ();
        closes = new ArrayList <Double> ();
        volumes = new ArrayList <Integer> ();
        adjCloses = new ArrayList <Double> ();

        //http://ichart.finance.yahoo.com/table.csv?s=IBM&d=5&e=5&f=2014&g=d&a=0&b=2&c=1962&ignore=.csv
        String url= "http://ichart.finance.yahoo.com/table.csv?s="+symbol+
                    "&a="+start.get(Calendar.MONTH)+
                    "&b="+start.get(Calendar.DAY_OF_MONTH)+
                    "&c="+start.get(Calendar.YEAR)+
                    "&d="+end.get(Calendar.MONTH)+
                    "&e="+end.get(Calendar.DAY_OF_MONTH)+
                    "&f="+end.get(Calendar.YEAR)+
                    "&g=d&ignore=.csv";

        try 
        {
            URL yhoofin = new URL(url);
            URLConnection data = yhoofin.openConnection();
            Scanner input = new Scanner(data.getInputStream());
            if(input.hasNext())
            {
                input.nextLine();
            }

            while(input.hasNextLine())
            {
                String line = input.nextLine();
                System.out.println(line);
            }
        }
        catch(Exception e)
        {
            System.err.println(e);
        }
    }

    public ArrayList<GregorianCalendar> getDates()
    {
        return dates;
    }

    /*public ArrayList<Double> getOpens()
    {}
    */
}

我只是将这个java类中的相同代码复制并粘贴到android中，并通过以下方式调用该方法。

GregorianCalendar start = new GregorianCalendar(Start_year, Start_month, Start_date);
                GregorianCalendar end = new GregorianCalendar(End_year, End_month, End_date);

                StockDownloader test = new StockDownloader("IBM" , start, end);

执行这两行后代码跳转到异常。

URLConnection data = yhoofin.openConnection();
Scanner input = new Scanner(data.getInputStream());