Access database connection using java

Question

I’m a beginner in java programming, and I’m trying to make a program that connects to a database and saves the information there. I created a specific class for the connection and created a method to insert the data, but it is falling in the catch and returning null. This code I found partial on the internet and changed to my need.

public void Insere(Cadastro cliente )
{
    if ((cliente.getNome() != null) && (cliente.getOS() != null) && (cliente.getDataEnt() != null) && (cliente.getMarca() != null) && (cliente.getModelo() != null) && (cliente.getNS() != null) && (cliente.getValor() != null) && (cliente.getDataOrc() != null))
    {
    try 
    {
        PreparedStatement strComandoSQL;
        strComandoSQL = conexao.prepareStatement("INSERT INTO Entrada(cod, Nome, Os, dataEnt, Marca, Modelo, NS, Valor, dataOrc) VALUES(?,'?','?','?','?','?','?','?','?')");
        strComandoSQL.setInt(1,cliente.getCod());
        strComandoSQL.setString(2,cliente.getNome());
        strComandoSQL.setString(3,cliente.getOS());
        strComandoSQL.setString(4,cliente.getDataEnt());
        strComandoSQL.setString(5,cliente.getMarca());
        strComandoSQL.setString(6,cliente.getModelo());
        strComandoSQL.setString(7,cliente.getNS());
        strComandoSQL.setString(8,cliente.getValor());
        strComandoSQL.setString(9,cliente.getDataOrc());
        int intRegistro = strComandoSQL.executeUpdate();
            if (intRegistro != 0){
            JOptionPane.showMessageDialog(null,"Registro adicionado !",
            "Mensagem",JOptionPane.INFORMATION_MESSAGE);
            comando.close();
            conexao.close();
            }
            else
            {
            JOptionPane.showMessageDialog(null,"Registro nao adicionado !",
            "Mensagem",JOptionPane.INFORMATION_MESSAGE);
            comando.close();
            conexao.close();
            }

}
catch (Exception Excecao) 
{
    JOptionPane.showMessageDialog(null,"SQLException: " +
    Excecao.getMessage(),"Erro: Selecao de registro",
    JOptionPane.INFORMATION_MESSAGE);
}
}
else
{
JOptionPane.showMessageDialog(null,"Falta Preencher Campo!",
"Mensagem",JOptionPane.INFORMATION_MESSAGE);
}
}

Does anyone know why it’s returning null?

The exception that is returning is "null"

The stack of errors:

java.lang.NullPointerException
    at planilha.Banco.Insere(Banco.java:52)
    at planilha.Planilha.actionPerformed(Planilha.java:102)
    at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
    at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
    at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
    at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
    at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
    at java.awt.Component.processMouseEvent(Component.java:6516)
    at javax.swing.JComponent.processMouseEvent(JComponent.java:3321)
    at java.awt.Component.processEvent(Component.java:6281)
    at java.awt.Container.processEvent(Container.java:2229)
    at java.awt.Component.dispatchEventImpl(Component.java:4872)
    at java.awt.Container.dispatchEventImpl(Container.java:2287)
    at java.awt.Component.dispatchEvent(Component.java:4698)
    at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
    at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
    at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
    at java.awt.Container.dispatchEventImpl(Container.java:2273)
    at java.awt.Window.dispatchEventImpl(Window.java:2719)
    at java.awt.Component.dispatchEvent(Component.java:4698)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:747)
    at java.awt.EventQueue.access$300(EventQueue.java:103)
    at java.awt.EventQueue$3.run(EventQueue.java:706)
    at java.awt.EventQueue$3.run(EventQueue.java:704)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
    at java.awt.EventQueue$4.run(EventQueue.java:720)
    at java.awt.EventQueue$4.run(EventQueue.java:718)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:717)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)

Here the method connects

public void Conecta()
{
    //JOptionPane.showMessageDialog(null, "Preparando para iniciar a conexão com o BD;");

try
{
    /* Tenta se conectar ao Driver */
    Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");

}
catch (ClassNotFoundException e)
{
    JOptionPane.showMessageDialog(null, "Impossível carregar o Driver.");
    System.exit(0);
}
try
{
    /* nomedobanco é o nome que você deu anteriormente ao seu alias */
    conexao = DriverManager.getConnection("jdbc:odbc:Camptecnica");
    comando = conexao.createStatement();

}
catch (SQLException sqle)
{
    JOptionPane.showMessageDialog(null, "Problema ao conectar!");
    System.exit(0);
}
 //JOptionPane.showMessageDialog(null, "Conectado com sucesso!");

}