DNA

package s_est_la_examinie;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.io.ObjectInputStream.GetField;
import java.util.Date;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;

public class C {
    private static final File fileIn = new File("input.txt");
    private static final File fileOut = new File("output.txt");
    private static HashMap<Key, HashSet<String>> map = new HashMap<Key, HashSet<String>>();

    public static void main(String[] args) throws IOException {
        long time = new Date().getTime();
        //
        run(args);
        //
        System.out.println("----------------------------");
        System.out.println(new Date().getTime() - time + " ms");
    }

    static void run(String[] args) throws IOException {

        System.out.println(fileIn.getAbsolutePath());
        BufferedReader in = new BufferedReader(new FileReader(fileIn));
        PrintWriter out = new PrintWriter(new FileWriter(fileOut));

        byte N = Byte.parseByte(in.readLine());
        String msg;
        int A,T,C,G;
        char a;
        for (int i = 0; i < N; i++) {
            msg = in.readLine();
            A = (int) msg.chars().filter(ch -> ch == 'A').count();
            T = (int) msg.chars().filter(ch -> ch == 'T').count();
            C = (int) msg.chars().filter(ch -> ch == 'C').count();
            G = (int) msg.chars().filter(ch -> ch == 'G').count();
            Key key = new Key(A, T, C, G);
            HashSet<String> list =  map.get(key);
            if (list == null) {
                list = new HashSet<String>();
                map.put(key, list);
            }
            list.add(msg);

        }
        in.close();
        out.println(map.size());
        for (HashSet<String> list : map.values()) {
            Iterator<String> iter = list.iterator();
            while (iter.hasNext()) {
                out.print(iter.next());
                if (iter.hasNext()) out.print(" ");
            }
            out.println();
        }
        out.close();

    }
}

class Key {
    private int A, T, C, G;

    public Key(int A, int T, int C, int G) {
        this.A = A;
        this.T = T;
        this.C = C;
        this.G = G;
    }

    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + A;
        result = prime * result + C;
        result = prime * result + G;
        result = prime * result + T;
        return result;
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        Key other = (Key) obj;
        if (A != other.A)
            return false;
        if (C != other.C)
            return false;
        if (G != other.G)
            return false;
        if (T != other.T)
            return false;
        return true;
    }
}