How can i put something in database?

package faq.server;

import java.util.ArrayList;
import java.util.concurrent.ConcurrentMap;

import org.mapdb.DB;

import faq.shared.Category;
import faq.shared.CategoryComponent;
import faq.shared.CategoryIterator;

import faq.shared.Question;

/**Classe che gestisce la memorizzazione delle domande
 *
 * Gestisce la memorizzazione di una nuova domanda all'interno dello stesso database 
 * che memorizza le categorie.
 * Permette di aggiungere o eliminare domande relative a una determinata categoria.
 * 
 *
 */
public class QuestionHandlerImpl 
{
	// Database
	private DB db;
	// Lista radici alberi categorie
	private ConcurrentMap<String, Category> categoryMap;
	// oggetto per la gestione delle categorie
	private CategoryHandlerImpl categoryHandler;
	
	public void clear(){
		categoryMap.clear();
		categoryHandler.clear();
	}
	public QuestionHandlerImpl( DB db, CategoryHandlerImpl categoryHandler)
	{
		this.db = db;
		this.categoryMap = this.db.getTreeMap("category");
		this.categoryHandler = categoryHandler;
		
	}
	
	public void addQuestion(Category category, Question question)
	{
		Category root = this.categoryMap.get("root");
		Category categoria = categoryHandler.getCategory(category.getName(), root);
		categoria.add(question);
		question.setCategory(categoria);
		categoryMap.replace("root", categoryMap.get("root"), root);
		this.db.commit();
	}
	
	public void removeQuestion(Category category, Question question)
	{
		Category root = this.categoryMap.get("root");
		Category categoria = categoryHandler.getCategory(category.getName(), root);
		categoria.remove(question);
		categoryMap.replace("root", categoryMap.get("root"), root);
		this.db.commit();
	}
	
	
	// Tutte le domande relative a una categoria
	public ArrayList<Question> getQuestions(Category category)
	{
		Category root = this.categoryMap.get("root");
		Category categoria = categoryHandler.getCategory(category.getName(), root);
		ArrayList<Question> res = new ArrayList<Question>();
		CategoryIterator sfogliaCategoria = (CategoryIterator) categoria.createIterator();
		while(sfogliaCategoria.hasNext())
		{
			CategoryComponent componente = (CategoryComponent) sfogliaCategoria.next();
			if( componente instanceof Question )
			{
				res.add( (Question)componente );
			}
			else
			{
				res.addAll(getQuestions((Category) componente));
			}
		}
		res.trimToSize();
		return res;
	}
	
	public ArrayList<Question> getAllQuestions()
	{
		Category root = this.categoryMap.get("root");
		return getQuestions(root);
	}
}

/**
 * 
 */
package faq.server;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.concurrent.ConcurrentMap;

import org.mapdb.DB;

import faq.shared.Answer;
import faq.shared.Category;
import faq.shared.Question;

/**Classe che gestisce la memorizzazione delle risposte
 *
 * Gestisce la memorizzazione di una nuova risposta all'interno dello stesso database 
 * che memorizza le domande e le categorie.
 * Permette di aggiungere o eliminare risposte relative a una determinata domanda.
 * 	
 *
 */
public class AnswerHandlerImpl 
{
	// Database
	private DB db;
	// Lista radici alberi categorie
	private ConcurrentMap<String, Category> categoryMap;
	
	public void clear() {
		categoryMap.clear();
		
	}
	
	public AnswerHandlerImpl( DB db)
	{
		this.db = db;
		this.categoryMap = this.db.getTreeMap("category");
	}	

	public void addAnswer(Question question, Answer answer)
	{
		Category root = this.categoryMap.get("root");
		question.addAnswer(answer);
		categoryMap.replace("root", categoryMap.get("root"), root);
		this.db.commit();
	}
	
	public void removeAnswer(Question question, Answer answer)
	{
		Category root = this.categoryMap.get("root");
		question.removeAnswer(answer);
		categoryMap.replace("root", categoryMap.get("root"), root);
		this.db.commit();
	}
	
	// Tutte le risposte relative a una domanda
	public ArrayList<Answer> getAnswers(Question question)
	{
		Category root = this.categoryMap.get("root");
		ArrayList<Answer> res = new ArrayList<Answer>();
		Iterator sfogliaDomanda = question.createIterator();
		while(sfogliaDomanda.hasNext())
		{
			res.add((Answer) sfogliaDomanda.next());			
		}
		res.trimToSize();
		return res;
	}
}

/**
 * 
 */
package faq.server;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.concurrent.ConcurrentMap;

import org.mapdb.DB;

import faq.shared.Answer;
import faq.shared.Category;
import faq.shared.Judgment;

/**Classe che gestisce la memorizzazione dei giudizi
 *
 * Gestisce la memorizzazione di un nuovo giudizio all'interno dello stesso database 
 * che memorizza le risposte, le domande e le categorie.
 * Permette di aggiungere giudizi relative a una determinata risposta.
 *
 *
 */
public class JudgmentHandlerImpl 
{
	// Database
	private DB db;
	// Lista radici alberi categorie
	private ConcurrentMap<String, Category> categoryMap;
	
	
	public void clear(){
		categoryMap.clear();
	}
	
	public JudgmentHandlerImpl( DB db)
	{
		this.db = db;
		this.categoryMap = this.db.getTreeMap("category");
	}	

	public void addJudgment(Answer answer, Judgment judgment)
	{
		Category root = this.categoryMap.get("root");
		answer.addJudgment(judgment);;
		categoryMap.replace("root", categoryMap.get("root"), root);
		this.db.commit();
	}
	
	// Tutte i giudizi relative a una risposta
	public ArrayList<Judgment> getJudgments(Answer answer)
	{
		//Category root = this.categoryMap.get("root");
		ArrayList<Judgment> res = new ArrayList<Judgment>();
		Iterator sfogliaRisposta = answer.createIterator();
		while(sfogliaRisposta.hasNext())
		{
			res.add((Judgment) sfogliaRisposta.next());			
		}
		res.trimToSize();
		return res;
	}
}

/*
 * Gestisce le operazioni sugli users
 */
public class LoginServiceImpl {
	
	// Database
	private DB db;
	// Lista utenti
	private ConcurrentMap<String, User> userMap;
	
	public LoginServiceImpl( DB db){
		this.db = db;
		this.userMap = this.db.getTreeMap("user");
		
		if( userMap.get("admin") == null){ // l'admin deve essere sempre presente nel db
			addAdmin();
		}
	}
	
	// Agigunge un utente al db, se gia'  presente lancia eccezione 
	public User addUser( String username, String password, String email, String name, String surname, String sex, String birthDate, String birthPlace, String address ) throws DuplicatedUserNameException {
		if( userMap.get( username ) != null ){
			throw new DuplicatedUserNameException( username );
		}
		else{
			User user = new NormalUser(username,password,email,name,surname,sex,birthDate,birthPlace,address);
			
			this.userMap.put( username, user );
			this.db.commit();
			return user;
		}
	}
	
	// Metodo che azzera la collezione utenti
	public void clear(){
		userMap.clear();
	}
	
	public void remove( String userName){
		userMap.remove( userName );
	}
	
	
	// Aggiunge l'utente admin
	public void addAdmin(){
		User admin = new AdminUser("admin", "admin", "admin@admin.com", null, null, null, null, null, null);
		userMap.put("admin", admin);
		this.db.commit();
	}

	// Controlla username e password, se l'utente non e' presente o la password e' sbagliata lancia eccezioni
	public User login(String userName, String password) throws WrongPasswordException, UserNotFoundException {
		User user = this.userMap.get( userName );
		if( user != null ){
			if( !user.getPassword().equals(password) ){
				throw new WrongPasswordException();
			}
		}
		else{
			throw new UserNotFoundException();
		}
		return user;
	}
	
	// Tutti gli utenti ( funzionalità admin )
		public ArrayList<User> getAllUsers(){
			ArrayList<User> res = new ArrayList<User>(userMap.values());
			return res;
		}
		
		// Tutti gli utenti non giudici o admin ( funzionalità admin )
		public ArrayList<User> getRegistered(){
			ArrayList<User> users = new ArrayList<User>( userMap.values() );
			ArrayList<User> res = new ArrayList<User>();
			for( User u : users ){
				if( u instanceof NormalUser ){
					res.add( u );
				}
			}
			res.trimToSize();
			return res;
		}
		
		// Nomina un giudice sostituendo l'istanza di utente normale 
		// con quella di utente giudice, associandola allo stesso nome
		public ArrayList<User> nominateJudge( String userName ){
			NormalUser normalToJudge = (NormalUser) userMap.get(userName);
			//judge.setRoleJudge();
			User judge = new JudgeUser(normalToJudge);
			userMap.replace(userName, normalToJudge, judge);
			this.db.commit();
			return getRegistered();
		}

		
		// Tutti gli utenti giudici ( funzionalità  admin )
		public ArrayList<User> getJudges(){
			ArrayList<User> users = new ArrayList<User>( userMap.values() );
			ArrayList<User> res = new ArrayList<User>();
			for( User u : users){
				if( u instanceof JudgeUser ){
					res.add( u );
				}
			}
			res.trimToSize();
			return res;
		}
}

package faq.shared;





import java.io.Serializable;
import java.util.ArrayList;
import java.util.Date;
import java.util.Iterator;

import com.google.gwt.i18n.shared.DateTimeFormat;

/**Classe per la gestione delle domande
 * 
 */
public class Question extends CategoryComponent implements Serializable
{
	/**
	 * 
	 */
	private static final long serialVersionUID = 1L;
	private String question;
	private RegisteredUser user;
	private Date date;
	private ArrayList<Answer> answers = new ArrayList<>();
	private Category category;
	
	public Category getCategory() {
		return category;
	}

	public void setCategory(Category category) {
		this.category = category;
	}

	public Question(){}
	
	public Question(String question, RegisteredUser user)
	{
		this.question=question;
		this.user=user;
		this.date= new Date();
	}
	
	public String getQuestion()
	{
		return question;
	}
	
	public User getUser()
	{
		return user;
	}
	
	public Date getDate()
	{
		return date;
	}
	
	public String getDay()
	{
		return DateTimeFormat.getFormat("yyyy-MM-dd").format(this.date);
		//DateTimeFormat fmt = DateTimeFormat.getFormat("EEEE, MMMM dd, yyyy");
	    //return fmt.format(this.date);
	     
	}
	
	public String getTime()
	{	
		return DateTimeFormat.getFormat("hh:mm").format(this.date);
	}
	
	public void addAnswer(Answer answer)
	{
		answers.add(answer);
	}
	
	public void removeAnswer(Answer answer)
	{
		answers.remove(answer);
	}
	
	public Answer getAnswer(int i)
	{
		return answers.get(i);
	}
	
	public Iterator<Object> createIterator()
	{
		return new AnswerIterator<>(answers);
	}
	
	@Override
	public int compareTo(Object o) {
		return getDate().compareTo(((Question) o).getDate());
	}
}

package faq.shared;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.Date;
import java.util.Iterator;

import com.google.gwt.i18n.shared.DateTimeFormat;

/**Classe che gestisce le risposte
 * 
 *
 */
public class Answer implements Collection, Comparable<Object>, Serializable
{
	/**
	 * 
	 */
	private static final long serialVersionUID = 1L;
	private String answer;
	private RegisteredUser user;
	private Date date;
	private ArrayList<Judgment> judgments = new ArrayList<>();
	
	public Answer(){}
	
	public Answer(String answer, RegisteredUser user)
	{
		this.answer=answer;
		this.user=user;
		this.date= new Date();
	}
	
	public String getAnswer()
	{
		return answer;
	}
	
	public User getUser()
	{
		return user;
	}
	
	public Date getDate()
	{
		return date;
	}
	
	public String getDay()
	{
		return DateTimeFormat.getFormat("yyyy-MM-dd").format(this.date);
		//DateTimeFormat fmt = DateTimeFormat.getFormat("EEEE, MMMM dd, yyyy");
	    //return fmt.format(this.date);
	     
	}
	
	public String getTime()
	{	
		return DateTimeFormat.getFormat("hh:mm").format(this.date);
	}
	
	public void addJudgment(Judgment judgment)
	{
		judgments.add(judgment);
	}
	
	public Judgment getJudgment(int i)
	{
		return judgments.get(i);
	}
	
	public double getEverageJudgment()
	{
		int total = 0;
		for(Judgment j : judgments)
		{
			total = total + j.getJudgment();
		}
		if(judgments.size() == 0)
		{
			return 0;
		}
		else
		{
			return total/judgments.size();
		}
	}

	@Override
	public Iterator<Object> createIterator() {
		
		return new JudgmentIterator<>(judgments);
	}

	@Override
	public int compareTo(Object o) {
		
		if (this.judgments.size() == 0)
		{
			return getDate().compareTo(((Answer) o).getDate());
		}
		else
		{
			if(this.getEverageJudgment() == ((Answer) o).getEverageJudgment())
			{
				return getDate().compareTo(((Answer) o).getDate());
			}
			else if(this.getEverageJudgment() > ((Answer) o).getEverageJudgment())
			{
				return 1;
			}
			else
			{
				return -1;
			}
		}
		
	}

}