Treat empty field even containing spaces

Question

I made a Celsius temperature converter for Fahrenheit, I’m willing to treat if in JTextField is different from 0, display the temperature in Fahrenheit, but appears 0.0 until empty, with spaces inserted in that field.

@Override
    public void actionPerformed(ActionEvent e) {

        double resultado = 0, valor1;

        if(e.getSource() == btnOk) {
            if(!text1.getText().isEmpty()) {
               try {
                   valor1 = Double.parseDouble(text1.getText()); 
                   resultado = valor1 * 1.8 + 32;

                }catch(NumberFormatException e1) {}
                    text2.setText(String.valueOf(resultado));
            }
        }

Answer 1

If the intention is not to let validate if the String is empty or with spaces only, try applying trim() to remove blanks:

@Override
    public void actionPerformed(ActionEvent e) {

        double resultado = 0, valor1;
        String fieldText = text1.getText().trim();

        if(e.getSource() == btnOk) {
            if(!fieldText.isEmpty()) {
               try {
                   valor1 = Double.parseDouble(fieldText); 
                   resultado = valor1 * 1.8 + 32;

                }catch(NumberFormatException e1) {}
                    text2.setText(String.valueOf(resultado));


   }

Obs.: Trim() does not remove whitespace between the characters of the string, only those that are at the beginning and end. If a string is passed only with whitespace for this method, the result will be an empty string.