Integer 类型中的方法 parseInt(String) 不适用于参数（布尔值）

Question

I am getting the error The method parseInt(String) in the type Integer is not applicable for the arguments (boolean)

Here is the code

} else if (Integer.parseInt(answerField.getText() == null)) {
                    JOptionPane.showMessageDialog(null, "You did not enter an answer!");
                }

I have also tried this but it doesn't work:

(Integer.parseInt(answerField.getText().equals("")))

&

(Integer.parseInt(answerField.getText().length()) == 0)

I just want to check to see if nothing has been entered and if so display a JOptionPane.

Edit: The var answerField is a JTextField, where the user inputs an answer of a mathematical question. So the ActionListener then determines if the answer is correct, hence the parseInt (because of it being a mathematical operation)

do {
        checkButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                if (Integer.parseInt(answerField.getText()) == correctAnswer) {
                    count++;
                    JOptionPane.showMessageDialog(null, "Correct");

                } else if (Integer.parseInt(answerField.getText().length()) == 0) {
                    JOptionPane.showMessageDialog(null, "You did not enter an answer!");
                } else {
                    count++;
                    JOptionPane.showMessageDialog(null, "Incorrect!");
                    System.exit(0);
                }
            }
        });
    } while (count < 11);

Answer 1

Lets analise the code you have

(Integer.parseInt(answerField.getText() == null))

the parameter

answerField.getText() == null

return a boolean and the method Integer.parseInt(bool) is not defined in the Integer class.

It looks like you want to do:

else if (someConditionHere) {
      Integer.parseInt(answerField.getText());
      JOptionPane.showMessageDialog(null, "You did not enter an answer!");
}

Answer 2

all of the values inside of your parse int method return a boolean becuase they are performing a comparison between two values that result in either true or false. You should use Boolean.parseBoolean() to return either "true" or "false" strings

Answer 3

Integer.parseInt(answerField.getText() == null) is evaluated as Integer.parseInt("someTextext" == null) then

Integer.parseInt(true/false)

Try to parse a boolean as an Integer will result as an error

To check is your field is null, only do if(answerField.getText() == null)

then if is not null you can try to parse the field value to an Integer the way you did.

Answer 4

I am not sure why you want to call Integer.parseInt, because you already have a boolean expression in your condition:

} else if (answerField.getText() == null) {
    JOptionPane.showMessageDialog(null, "You did not enter an answer!");
}

Note that if conditions in Java can only accept boolean expressions, and you couldn't pass in an integer or whatever else you'd think of as truthy or falsy (unlike C or Javascript, for example).

Answer 5

If all you want to do is check to see if there's some string contained in answerField , then all you need to do is check to see if it's not null or empty.

if(!("".equals(answerField.getText()) || null == answerField.getText()) {
    // other, non-integer-handling code here
}

You do not want to handle parsing the integer if there's an empty string or if it's null , since that could result in a NullPointerException .