Java - Check If Jtextfield Is Empty or Not

Java - Check if JTextField is empty or not

For that you need to add change listener (a DocumentListener which reacts for change in the text) for your JTextField, and within actionPerformed(), you need to update the loginButton to enabled/disabled depending on the whether the JTextfield is empty or not.

Below is what I found from this thread.

yourJTextField.getDocument().addDocumentListener(new DocumentListener() {
  public void changedUpdate(DocumentEvent e) {
    changed();
  }
  public void removeUpdate(DocumentEvent e) {
    changed();
  }
  public void insertUpdate(DocumentEvent e) {
    changed();
  }

  public void changed() {
     if (yourJTextField.getText().equals("")){
       loginButton.setEnabled(false);
     }
     else {
       loginButton.setEnabled(true);
    }

  }
});

How to check if a JTextField is empty?

JTextField#getText#isEmpty...

if (tf1.getText().trim().isEmpty()) {
    ...
}

It's been a very long time since JTextFiels#getText could return null

You might also like to have a look at Validating Input which would probably be significantly easier

Checking if JTextField not empty

Take...

if (text.getText().equals("")) {
    JOptionPane.showMessageDialog(rootPane, "Please enter anything");
}

and put it inside you actionPerformed method...

btn1.addActionListener(new ActionListener() {

    @Override
    public void actionPerformed(ActionEvent e) {
        if (text.getText().equals("")) {
            JOptionPane.showMessageDialog(rootPane, "Please enter anything");
        }
        JOptionPane.showMessageDialog(rootPane, "Hello : " + text.getText());
    }
});

How to Check if all the JTexFields are empty or not?

Store your text fields in a List so that you can iterate over them later.

public class ClassContainingTextFields {
    private final ArrayList<JTextField> textFields = new ArrayList<>();

    // ... inside the method that creates the fields ...
        for (int i = 0; i < 9; i++) {
            JTextField field = new JTextField(3);
            //  .. do other setup 
            textFields.add(field);
        }


    /**
     * This method returns true if and only if all the text fields are empty
     **/
    public boolean allFieldsEmpty() {
        for (JTextField textbox : textFields) {
            if (! textbox.getText().trim().isEmpty() ) {
                return false;   // one field is non-empty, so we can stop immediately
            }
        }
        return true;  // every field was empty (or else we'd have stopped earlier)
    }
    // ....
}

How to check if textfield is empty?

First of all, check if user_name is not null. If it is not, you are setting a null text value to the JavaFX component somewhere in your code.

if(user_name.getText().trim().isEmpty()){

In any case, applying the trim() to a null value is what causes your exception. You should not need this (see Uluk Biy's comment to this answer), but considering you created a user_name TextField, you must check first if the getText() method is not null.

Something like this should do the trick:

if (user_name.getText() == null || user_name.getText().trim().isEmpty()) {
     // your code here
}

Checking a JTextfield is not empty

Your problem is the content of the while loop:

while (breakSwitch = true) {
    if (nameField.getText().isEmpty()) {
        errorReportField.setText("name error");
        break;
    }
    // stuff omitted
    if (e.getSource() == addVolumeButton) {
        // stuff omitted
        nameField.setText("");
        // stuff omitted
    }
    if (e.getSource() == addNumberButton) {
        // stuff omitted
        nameField.setText("");
        // stuff omitted
    }
    errorReportField.setText("");
}

First of all: you've created a loop with an assignment instead of a boolean comparison.
And now the problem: if e.getSource() is either addVolumeButton or addNumberButton, then you're removing the content of nameField. In the next iteration of your loop you're testing if nameField.getText().isEmpty(), which return true now. You'll now get the error and exit the loop there.

How to fix the problem? I recommend to think about that loop, because I'm relatively sure, that it is unnecessary to loop there.

A version of your actionPerformed method without the loop could look like this:

@Override
public void actionPerformed(ActionEvent e) {
    if (nameField.getText().isEmpty()) {
        errorReportField.setText("name error");
        return; // error occured; exit the method early
    }
    try {
        price = Integer.parseInt(priceField.getText());
    } catch (NumberFormatException exception) {
        errorReportField.setText("price error");
        priceField.setText("");
        return; // error occured; exit the method early
    }
    try {
        number = Integer.parseInt(numberField.getText());
    } catch (NumberFormatException exception) {
        errorReportField.setText("number error");
        numberField.setText("");
        return; // error occured; exit the method early
    }
    if (e.getSource() == addVolumeButton) {
        // omitted
    }
    if (e.getSource() == addNumberButton) {
        // omitted
    }
    errorReportField.setText("");
}

This version uses the code word return; to exit the current method if an error occured.

How to point out which jTextfield is empty

Do something like below:

public void checkEmpty() {
    JTextField [] textFields = {jTextField1,jTextField2,jTextField3,jTextField4,jTextField5,jTextField6};
    isInputValid = true;
    for (int i = 0; i < textFields.length; i++) {
        JTextField jTextField = textFields[i];
        String textValue = jTextField.getText().trim();
        if (textValue.length() == 0) {
            //turn background into red
            jTextField.setBackground(Color.RED);
            isInputValid = false;
        }
    }

    // now check if input are valid
    if(!isInputValid) return;

    //save to database----> I know what I have to do here.
}

Checking whether JTextFields are empty

You should stick with creating a method that checks all the text fields using if statements and returns a boolean.

private boolean checkFields(){
        if(textField1.getText().lenght()<1)
            return false;
        if(textField2.getText().lenght()<1)
            return false;
        //check all text fields

        return true;
}

The method representing your button action will first call the checkFields() method and if true is returned continue else return after it informs the user that not all text fields were filled.

private void buttonAction(){
        if(!checkFields()){
            Alert message=new Alert(        Alert.AlertType.WARNING);
            message.setHeaderText("Text field empty");
            message.setContentText("One of the text fields is empty");
            message.showAndWait();
            return;
        }

        //continue the method
    }

If you ensure that the method will only run if all the TextFields have text there is nothing to worry. Exceptions are much more costly to throw and catch and should be used in exceptional cases.

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