Java - SQLite database locked

I'm heaving a problem with SQLite and Java.

I don't know if it's because I'm leaving some open connection (or PreparedStatement/ResultSet) or if it's because I'm handling the Connection in a wrong way but this code is giving me a hard time for the past 2 days.

I've created the above class to create the connection the SQLite DB:

package lp2.database;

import java.sql.*;

public class ConnectionFactory
{
    public Connection getConnection()
    {
        Connection c = null;

        try
        {
            System.out.println("Conectando ao banco de dados...");
            Class.forName("org.sqlite.JDBC");
            c = DriverManager.getConnection("jdbc:sqlite:src/lp2/database/rivieraresort.db");
            System.out.println("Conectado com sucesso!");
        }
        catch(Exception e)
        {
            e.printStackTrace();
        }

        return c;
    }
}

And the following one to handle the DB itself package lp2.database;

import lp2.objetos.*;

import java.sql.*;
import java.util.Arrays;
import java.util.List;
import java.util.ArrayList;

public class RivieraDB
{
    public void adicionarCliente(Cliente cliente) throws Exception
    {
        Connection c = new ConnectionFactory().getConnection();
        String query = "INSERT INTO clientes (nome, cpf, endereco, nascimento, cartao, contrato_id, status_hospedagem) VALUES (?, ?, ?, ?, ?, ?, ?)";
        PreparedStatement pstmt = c.prepareStatement(query);

        pstmt.setString(1, cliente.getNome());
        pstmt.setString(2, cliente.getCpf());
        pstmt.setString(3, cliente.getEndereco());
        pstmt.setString(4, cliente.getNascimento());
        pstmt.setString(5, cliente.getCartao());
        pstmt.setInt(6, cliente.getContrato().getID());
        pstmt.setBoolean(7, cliente.getEstaHospedado());

        pstmt.execute();
        pstmt.close();
        c.close();
    }

    public void adicionarContrato(Contrato contrato) throws Exception
    {
        Connection c = new ConnectionFactory().getConnection();
        String query = "INSERT INTO contratos (gastos, multa, data_inicio, tempo) VALUES (?, ?, ?, ?)";
        PreparedStatement pstmt = c.prepareStatement(query);

        pstmt.setDouble(1, contrato.getGastos());
        pstmt.setDouble(2, contrato.getMulta());
        pstmt.setString(3, contrato.getInicioContrato());
        pstmt.setInt(4, contrato.getDias());

        pstmt.execute();
        pstmt.close();
        c.close();
    }

    public void adicionarQuarto(Quarto quarto) throws Exception
    {
        Connection c = new ConnectionFactory().getConnection();
        String query = "INSERT INTO quartos (tipo, camas_extras, preco, contrato_id) VALUES (?, ?, ?, ?)";
        PreparedStatement pstmt = c.prepareStatement(query);

        pstmt.setString(1, quarto.getTipo());
        pstmt.setInt(2, quarto.getCamasExtras());
        pstmt.setDouble(3, quarto.getPagamento());
        pstmt.setInt(4, quarto.getContratoID());

        pstmt.execute();
        pstmt.close();
        c.close();
    }

    public Quarto buscarQuarto(int contratoID) throws Exception
    {
        Quarto quartoEncontrado = null;

        Connection c = new ConnectionFactory().getConnection();
        c = new ConnectionFactory().getConnection();
        String query = "SELECT * FROM quartos WHERE contrato_id = ?";
        PreparedStatement pstmt = c.prepareStatement(query);

        pstmt.setInt(1, contratoID);

        ResultSet rs = pstmt.executeQuery();

        while(rs.next())
        {
            String tipo = rs.getString("tipo");
            int camasExtras = rs.getInt("camas_extras");
            double preco = rs.getDouble("preco");

            quartoEncontrado = new Quarto(tipo, camasExtras, preco);
        }

        rs.close();
        pstmt.close();
        c.close();
        return quartoEncontrado;
    }

    public Contrato buscarContrato(int contratoID) throws Exception
    {
        Contrato contratoEncontrado = null;

        Connection c = new ConnectionFactory().getConnection();
        Quarto quartoAssociado = buscarQuarto(contratoID);
        c = new ConnectionFactory().getConnection();
        String query = "SELECT * FROM contratos WHERE id = ?";
        PreparedStatement pstmt = c.prepareStatement(query);

        pstmt.setInt(1, contratoID);

        ResultSet rs = pstmt.executeQuery();

        while(rs.next())
        {
            String inicioContrato = rs.getString("data_inicio");
            int tempo = rs.getInt("tempo");

            contratoEncontrado = new Contrato(quartoAssociado, inicioContrato, tempo);
        }

        rs.close();
        pstmt.close();
        c.close();
        return contratoEncontrado;
    }

    public ArrayList<Cliente> getClientes() throws Exception
    {
        ArrayList<Cliente> clientesEncontrados = new ArrayList<Cliente>();
        Cliente clienteEncontrado = null;
        Connection c = new ConnectionFactory().getConnection();
        String query = "SELECT * FROM clientes";
        PreparedStatement pstmt = c.prepareStatement(query);

        ResultSet rs = pstmt.executeQuery();

        while(rs.next())
        {
            String nome = rs.getString("nome");
            String cpf = rs.getString("cpf");
            String nascimento = rs.getString("nascimento");
            String endereco = rs.getString("endereco");
            String cartao = rs.getString("cartao");
            int contratoID = rs.getInt("contrato_id");
            boolean statusHospedagem = rs.getBoolean("status_hospedagem");

            clienteEncontrado = new Cliente(nome, cpf, nascimento, endereco);
            clienteEncontrado.setCartao(cartao);
            clienteEncontrado.setContrato(buscarContrato(contratoID));
            clienteEncontrado.setEstaHospedado(statusHospedagem);

            clientesEncontrados.add(clienteEncontrado);
        }

        rs.close();
        pstmt.close();
        c.close();
        return clientesEncontrados;
    }
}

The "[SQLITE_BUSY] The database file is locked (database is locked)" error only occurs when I try to use the getClientes() method.

Any ideas?