JavaFX Sqlite检查TextField是否为空(JavaFX Sqlite check TextField wether its empty)

 我现在正在努力检查我的所有InputFields他们== "" 。 
 
 我在这里找到了很多解决方案但不知何故它不起作用。 
 
 我有一个RegistrationModal和一个RegistrationController。 
 
 在模态中，我试图检查这样的字段： 
 
public boolean RegisterUser(String user, String vorname, String nachname) throws SQLException {

    PreparedStatement preparedStatement = null;

    if (user == "" || vorname == "" || nachname == "") {
        System.out.println("Fill in all fields");
        return false;
    }
// Here follows the SQL query the prepared statement and exequte
}
 
 但它永远不会使用这个if语句，我不知道为什么？ 
 
 我还尝试捕获控制器中的空元素： 
 
public void Absenden(ActionEvent event) {
    try {
        if (registerModel.RegisterUser(txt_user.getText(), txt_vorname.getText(),
                txt_nachname.getText())) {


            if (registerModel.RegisterUser(txt_user.getText().trim().isEmpty(), txt_vorname.getText().trim().isEmpty(),
                    txt_nachname.getText().trim().isEmpty())) {
                System.out.println("False! Do something?");
            }


            // Here opens the new window with a notification Registration was successfull
            ((Node) event.getSource()).getScene().getWindow().hide();
}
 
 在这里我有错误，这就是为什么两个if语句已经看起来很奇怪，我不得不在模型中自动生成一个新方法，使其与布尔值一起使用，但它仍然从未使用过这个if语句。 
 
 我试着只提供相关代码，否则会更多。 
 
 也许有人有个主意。 
 
 谢谢 

I am struggling right now to check all my InputFields wether they == "".
 
I found many solutions here but somehow it doesnt work.
 
I have a RegistrationModal and a RegistrationController.
 
In the modal I tryed to check the fields like that:
 
public boolean RegisterUser(String user, String vorname, String nachname) throws SQLException {

    PreparedStatement preparedStatement = null;

    if (user == "" || vorname == "" || nachname == "") {
        System.out.println("Fill in all fields");
        return false;
    }
// Here follows the SQL query the prepared statement and exequte
}
 
But it it never uses this if statement, I have no idea why?
 
I also tryed to catch the empty element in the controller:
 
public void Absenden(ActionEvent event) {
    try {
        if (registerModel.RegisterUser(txt_user.getText(), txt_vorname.getText(),
                txt_nachname.getText())) {


            if (registerModel.RegisterUser(txt_user.getText().trim().isEmpty(), txt_vorname.getText().trim().isEmpty(),
                    txt_nachname.getText().trim().isEmpty())) {
                System.out.println("False! Do something?");
            }


            // Here opens the new window with a notification Registration was successfull
            ((Node) event.getSource()).getScene().getWindow().hide();
}
 
Here I had errors so thats why two if statement which already seems weird, I had to autogenerate a new method in model to make this work with booleans, but still it never used this if statement.
 
I tryed to give only relevant code, otherwise it would be much more.
 
Maybe someone has an idea.
 
Thanks

原文：https://stackoverflow.com/questions/36134119