Computing GC Content - Without TreeMap

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("output.txt");

        String maxID = "";
        double maxGC = 0.0;

        while (in.hasNextLine()) {
            String currentID = in.nextLine();
            String currentDNA = "";
            while (in.hasNextLine() && !in.hasNext(">.*")) {
                currentDNA += in.nextLine();
            }
            double currentGC = getGCContent(currentDNA);
            if (currentGC > maxGC) {
                maxID = currentID;
                maxGC = currentGC;
            }
        }

        out.println(maxID + " " + maxGC);

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