Computing GC Content

import java.util.*;
import java.io.*;

public class ComputeGCContent {

    private static Double getGCContent(String dna) {
        int gc = 0;
        for (char symbol : dna.toCharArray()) {
            if (symbol == 'G' || symbol == 'C') {
                gc++;
            }
        }
        return (double) gc / dna.length() * 100;
    }

    public static void main(String[] args) throws IOException {

        Scanner in = new Scanner(new File("input.txt"));
        PrintWriter out = new PrintWriter(new File("output.txt"));

        TreeMap<Double, String> data = new TreeMap<Double, String>();

        while (in.hasNextLine()) {
            String id = in.nextLine();
            data.put(getGCContent(in.nextLine()), id);
        }

        out.println(data.lastEntry().getValue() + " " + data.lastKey());

        in.close();
        out.close();
    }

}