線程“ AWT-EventQueue-0”中的異常java.lang.NumberFormatException：空

Question

有人可以幫助我嗎？ 我在Netbeans中遇到了這個異常

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)

這是我的代碼的一部分，可能會導致異常：

   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); 
        }
}   

誰能告訴我如何解決？ 謝謝

Answer 1

您必須檢查costmeal.getText（）和qtypizza.getText（）均包含有效數字，根據快照代碼和堆棧跟蹤，似乎其中之一為空。

Answer 2

NumberFormatException是當您嘗試將String轉換為數字（int，double，float等）時可能引發的異常。 您必須通過將代碼放在try catch中或將異常添加到方法簽名中來處理異常。

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); 
    }
}   

要么

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();
    }
}