java.lang.NumberFormatException: empty String

Question

The code below keeps giving a `java.lang.NumberFormatException: empty String`: ``` private void jButton4ActionPerformed(java.awt.event.ActionEvent evt) { double AText = Double.parseDouble(angleAField.getText()); double BText = Double.parseDouble(angleBField.getText()); double CText = Double.parseDouble(angleCField.getText()); double aText = Double.parseDouble(sideaField.getText()); double bText = Double.parseDouble(sidebField.getText()); double cText = Double.parseDouble(sidecField.getText()); if (getMissing(angleAField.getText()) == false && getMissing(angleCField.getText()) == false) { //doesnt have angle C ,find Angle A double angleA = Math.round(Math.asin((Math.sin(BText) / bText) * aText)); angleAField.setText("" + angleA); } } public boolean getMissing(String Field) { try { if (Field.equals("")) { return false; // has number } } catch (NumberFormatException e) {} return true; } ``` Error: ``` Exception in thread "AWT-EventQueue-0" java.lang.NumberFormatException: empty String at…

Accepted Answer

You should check your field before parse double:

```
private void jButton4ActionPerformed(java.awt.event.ActionEvent evt) {
   double AText = ParseDouble(angleAField.getText());
   double BText = ParseDouble(angleBField.getText());
   double CText = ParseDouble(angleCField.getText());
   double aText = ParseDouble(sideaField.getText());
   double bText = ParseDouble(sidebField.getText());
   double cText = ParseDouble(sidecField.getText());

// other code here same
}

double ParseDouble(String strNumber) {
   if (strNumber != null && strNumber.length() > 0) {
       try {
          return Double.parseDouble(strNumber);
       } catch(Exception e) {
          return -1;   // or some value to mark this field is wrong. or make a function validates field first ...
       }
   }
   else return 0;
}
```

java.lang.NumberFormatException: empty String

Solution

Problem