I have a hard time submitting my first piece of code. Compilation error appeared and I have no idea why. The following is my code.

import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

/**
 * Created by Tanya on 2016/9/5.
 */
public class ReverseRoot2
{
    Scanner in;
    PrintWriter out;
    public void work()throws Exception
    {
        List<Double> numlist = new ArrayList<Double>();
        in = new Scanner(System.in);
        String line = "";
        while(in.hasNextLine() && !(line = in.nextLine()).equals(""))
        {
            String[] strnums = line.split(" ");
            for(String strnum : strnums)
            {
                if(strnum.matches("[0-9]+\\.*[0-9]*"))
                {
                    numlist.add(Double.parseDouble(strnum));
                }
            }
        }
        out = new PrintWriter(System.out);
        int len = numlist.size();
        for(int i = len - 1;i>=0;i--)
        {
            out.print(Math.sqrt(numlist.get(i).doubleValue()) + "\t");
        }
        out.flush();
    }
    static public void main(String[] args)throws Exception
    {
        ReverseRoot2 rr = new ReverseRoot2();
        rr.work();
    }
}