Garder une structure de donnée en mémoire

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.Arrays;
import java.util.List;
import java.util.Map;
import java.util.TreeMap;

public class Dictionnaire
{
    public static final String DICO_FILEPATH = "C:/dico.ser";
    
    private static Map<String, List<String>> dico = null;
    
    public static Map<String, List<String>> getDictionnaire()
    {
        if (dico == null)
            dico = deserialiser();
        
        if (dico == null)
        {
            dico = construire();
            serialiser();
        }
        
        return dico;
    }
    
    private static Map<String, List<String>> construire() // TODO
    {
        Map<String, List<String>> map = new TreeMap<String, List<String>>();
            map.put("a",Arrays.asList("a","à","â","ä"));
            map.put("e",Arrays.asList("e","è","ê","ë"));
        return map;
    }
    
    private static void serialiser()
    {
        try
        {
            ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(DICO_FILEPATH));
            oos.writeObject(dico);
            oos.close();
        } 
        catch (Exception e) 
        {
        }
    }
    
    @SuppressWarnings("unchecked")
    private static Map<String, List<String>> deserialiser()
    {
        try
        {
            ObjectInputStream ois = new ObjectInputStream(new FileInputStream(DICO_FILEPATH));
            dico = (Map<String, List<String>>) ois.readObject();
            ois.close();
            return dico;
        }
        catch (Exception e)
        {
            return null;
        }
    }
    
    public static void main(String[] args)
    {
        System.out.println(Dictionnaire.getDictionnaire());
    }
}