setFirstResult Hibernate () выпускают с Oracle jdbc драйвер

Вам нужно вызвать getPassword() в методе actionPerformed().

 public void actionPerformed(ActionEvent event)
    {
        enteredPassword = new String(masterPasswordField.getPassword());
        if(enteredPassword.equals(masterPassword))
        {
            JOptionPane.showConfirmDialog(null, "Correct");
            //close the masterPasswordFrame and take the user to the Password Vault
        }
        else
        {
            JOptionPane.showConfirmDialog(null, "Password Incorrect. Please Try Again.");
        }
    }