线程“ AWT-EventQueue-0”中的异常java.lang.NumberFormatException：空

Question

anyone can help me? I got this exception in Netbeans

Exception in thread "AWT-EventQueue-0" java.lang.NumberFormatException: 
empty 
String
at sun.misc.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:1842)
at sun.misc.FloatingDecimal.parseDouble(FloatingDecimal.java:110)
at java.lang.Double.parseDouble(Double.java:538)

and this is part of my code that probably makes the exception :

   private void pizzaMouseClicked(java.awt.event.MouseEvent evt) {                                        
   double cMeal = Double.parseDouble(costmeal.getText());
   double qPizza = Double.parseDouble(qtypizza.getText());
   double cPizaa = 6000;


        if(pizza.isSelected())
        {
        i[0] = (qPizza * cPizaa) + cMeal;
        String pMeal = String.format("%.2f", i[0]);
        costmeal.setText(pMeal); 
        }
}   

Can anyone tell me how to fix it? Thank you

Answer 1

您必须检查costmeal.getText（）和qtypizza.getText（）均包含有效数字，根据快照代码和堆栈跟踪，似乎其中之一为空。

Answer 2

NumberFormatException is an Exception that might be thrown when you try to convert a String into a number(int, double, float etc..). You have to handle the exception either by putting the code inside try catch or add the exception to the method signature.

private void pizzaMouseClicked(java.awt.event.MouseEvent evt) throws NumberFormatException {                                        
   double cMeal = Double.parseDouble(costmeal.getText());
   double qPizza = Double.parseDouble(qtypizza.getText());
   double cPizaa = 6000;
   if(pizza.isSelected())
   {
       i[0] = (qPizza * cPizaa) + cMeal;
       String pMeal = String.format("%.2f", i[0]);
       costmeal.setText(pMeal); 
    }
}   

Or

private void  pizzaMouseClicked(java.awt.event.MouseEvent evt) {       
    try{                                 
        double cMeal = Double.parseDouble(costmeal.getText());
        double qPizza = Double.parseDouble(qtypizza.getText());
        double cPizaa = 6000;


        if(pizza.isSelected())
        {
            i[0] = (qPizza * cPizaa) + cMeal;
            String pMeal = String.format("%.2f", i[0]);
           costmeal.setText(pMeal); 
    }
    }
    catch(NumberFormatException e){
        e.printStackTrace();
    }
}