Parameter Index Out of Range

//MÉTODO QUE BUSCA NO BANCO
public void validateUser(Administrator adm)
    {
        PreparedStatement p = null;
        ResultSet rs = null;

        Connection c = new dbConnections().openConnection();

        String sql = "SELECT `username_adm`, `password_adm`\n" +
                     "FROM `tb_adm` \n" +
                     "WHERE username_adm = '?' AND password_adm = '?'";

        try
        {
            p = c.prepareStatement(sql);
            p.setString(1, adm.getUsername());
            p.setString(2, adm.getPassword());

            rs = p.executeQuery();

            if(rs.next())
            {
                System.out.println("Usuário validado com sucesso!");
                adminMenu sc = new adminMenu();
                sc.setVisible(true);
            }
            else
            {
                System.out.println("Erro ao validar usuário!");
                JOptionPane.showMessageDialog(null, "Usuário ou senha inválidos!\n"
                        + "Por favor, tente novamente.");
            }
        }
        catch (SQLException ex)
        {
            Logger.getLogger(sqlOperations.class.getName()).log(Level.SEVERE, null, ex);
        }


    }

//CÓDIGO DENTRO DA INTERFACE DE LOGIN
private Administrator adm = new Administrator();

    private void passPFieldActionPerformed(java.awt.event.ActionEvent evt) {
        // TODO add your handling code here:
        //String username = loginField.getText();

    }

    private void loginFieldActionPerformed(java.awt.event.ActionEvent evt) {
        // TODO add your handling code here:
        //String password = passPField.getText();

    }

    private void enterButtonActionPerformed(java.awt.event.ActionEvent evt) {
        // TODO add your handling code here:
        String username = loginField.getText();
        String password = passPField.getText();
        adm.setUsername(username);
        adm.setPassword(password);

        sqlOperations op = new sqlOperations();
        op.validateUser(adm);

        System.out.println("Fim da execução do botão 'entrar'");
    }

//EXCEPTION======================================================================================>
Execução 'dbConnection.openConnection();' entrou no 'try'.
Conexão estabelecida com sucesso!
Fim da execução do botão 'entrar'
set 15, 2015 10:52:06 AM com.nanothings.ProjetoEGD.models.sqlOperations validateUser
GRAVE: null
java.sql.SQLException: Parameter index out of range (1 > number of parameters, which is 0).
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1074)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:988)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:974)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:919)
    at com.mysql.jdbc.PreparedStatement.checkBounds(PreparedStatement.java:3813)
    at com.mysql.jdbc.PreparedStatement.setInternal(PreparedStatement.java:3795)
    at com.mysql.jdbc.PreparedStatement.setString(PreparedStatement.java:4616)
    at com.nanothings.ProjetoEGD.models.sqlOperations.validateUser(sqlOperations.java:76)
    at com.nanothings.ProjetoEGD.views.Login.enterButtonActionPerformed(Login.java:156)
    at com.nanothings.ProjetoEGD.views.Login.access$200(Login.java:18)
    at com.nanothings.ProjetoEGD.views.Login$3.actionPerformed(Login.java:72)
    at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2022)
    at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2348)
    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:6535)
    at javax.swing.JComponent.processMouseEvent(JComponent.java:3324)
    at java.awt.Component.processEvent(Component.java:6300)
    at java.awt.Container.processEvent(Container.java:2236)
    at java.awt.Component.dispatchEventImpl(Component.java:4891)
    at java.awt.Container.dispatchEventImpl(Container.java:2294)
    at java.awt.Component.dispatchEvent(Component.java:4713)
    at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4888)
    at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4525)
    at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4466)
    at java.awt.Container.dispatchEventImpl(Container.java:2280)
    at java.awt.Window.dispatchEventImpl(Window.java:2750)
    at java.awt.Component.dispatchEvent(Component.java:4713)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:758)
    at java.awt.EventQueue.access$500(EventQueue.java:97)
    at java.awt.EventQueue$3.run(EventQueue.java:709)
    at java.awt.EventQueue$3.run(EventQueue.java:703)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:86)
    at java.awt.EventQueue$4.run(EventQueue.java:731)
    at java.awt.EventQueue$4.run(EventQueue.java:729)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:728)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)