Jtextfield入力からダブル/ Intを解析する

Question

私はJavaで新しく、JTextfieldを使用してユーザーから値を受け取るプログラムを作成しようとしています。コンパイルしようとすると、JTextfieldにNumberFormatExceptionエラー があるという問題が発生しました。ここに私のコードは次のとおりです。

import javax.swing.*; 
import java.lang.*; 
public class VehicleParking { 
    public static void main(String args[]) { 
     JTextField inh = new JTextField(2); 
     JTextField inm = new JTextField(2); 
     JTextField outh = new JTextField(2); 
     JTextField outm = new JTextField(2); 

     JPanel InPanel = new JPanel(); 
     InPanel.add(new JLabel("In Hours: ")); 
     InPanel.add(inh); 
     String inhour = inh.getText(); 
     double inhourInput = Double.valueOf(inhour); 
     InPanel.add(Box.createHorizontalStrut(15)); 
     InPanel.add(new JLabel("Minutes :")); 
     InPanel.add(inm); 
     String inminute = inm.getText(); 
     double inminuteInput = Double.valueOf(inminute); 

     JPanel OutPanel = new JPanel(); 


     OutPanel.add(new JLabel("Out Hours: ")); 
     OutPanel.add(outh); 
     String outhour = outh.getText(); 
     double outhourInput = Double.valueOf(outhour); 
     OutPanel.add(Box.createHorizontalStrut(15)); 
     OutPanel.add(new JLabel("Minutes :")); 
     OutPanel.add(outm); 
     String outminute = outm.getText(); 
     double outminuteInput = Double.valueOf(outminute); 

そして、ここでは、私はそれをコンパイルしようとすると、私が得るものです：

Exception in thread "main" 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) 
    at java.lang.Double.valueOf(Double.java:502) 
    at VehicleParking.main(VehicleParking.java:23) 

あり、ディスプレイや算術目的のために下部によります。 また、tryとcatchを使用しようとしましたが、問題はまったく解決しません（さらにエラーが表示されました）。数値書式の例外の問題。（私はそれが何らかの形でこのような単純な算術演算プログラムには長すぎることを知っている。申し訳ありません。）

import javax.swing.*; 
import java.lang.*; 
public class VehicleParking { 
    public static void main(String args[]) { 
     JTextField inh = new JTextField(2); 
     JTextField inm = new JTextField(2); 
     JTextField outh = new JTextField(2); 
     JTextField outm = new JTextField(2); 

     JPanel InPanel = new JPanel(); 
     InPanel.add(new JLabel("In Hours: ")); 
     InPanel.add(inh); 
     InPanel.add(Box.createHorizontalStrut(15)); 
     InPanel.add(new JLabel("Minutes :")); 
     InPanel.add(inm); 

     JPanel OutPanel = new JPanel(); 


     OutPanel.add(new JLabel("Out Hours: ")); 
     OutPanel.add(outh); 
     OutPanel.add(Box.createHorizontalStrut(15)); 
     OutPanel.add(new JLabel("Minutes :")); 
     OutPanel.add(outm); 




     int choice = JOptionPane.showConfirmDialog(null, InPanel, "Vehicle Parking System",JOptionPane.OK_CANCEL_OPTION); 
      if (choice == JOptionPane.OK_OPTION) 
       { 
        try 
         {String inhour = inh.getText(); 
         double inhourInput = Double.valueOf(inhour);} 
        catch (NumberFormatException e){ 
         if (inhour == null || inhour.equals("")) 
          {inhourInput = 0.0;} 
         else 
          {inhourInput = 0.0;}} 


        try 
         {String inminute = inm.getText(); 
         double inminuteInput = Double.valueOf(inminute);} 
        catch (NumberFormatException e){ 
         if (inminute == null || inminute.equals("")) 
          {inminuteInput = 0.0;} 
         else 
          {inminuteInput = 0.0;}} 

        int choice2 = JOptionPane.showConfirmDialog(null, OutPanel, "Vehicle Parking System",JOptionPane.OK_CANCEL_OPTION); 
        if (choice2 == JOptionPane.OK_OPTION) 
         { 
          try 
           {String outhour = outh.getText(); 
           double outhourInput = Double.valueOf(outhour);} 
          catch (NumberFormatException e){ 
           if (outhour == null || outhour.equals("")) 
            {outhourInput = 0.0;} 
           else 
            {outhourInput = 0.0;}} 

          try 
           {String outminute = outm.getText(); 
           double outminuteInput = Double.valueOf(outminute);} 
          catch (NumberFormatException e){ 
           if (outminute == null || outminute.equals("")) 
            {outminuteInput = 0.0;} 
           else 
            {outminuteInput = 0.0;}} 
         double hour = outhourInput - inhourInput; 
         double minute = outminuteInput - inminuteInput; 
         String[] VehicleType = {"Car","Van","Bus","Lorry"}; 
         String typeVehicle =(String)JOptionPane.showInputDialog (null, "Choose vehicle type: ","Vehicle Parking System",JOptionPane.PLAIN_MESSAGE, 
                       null,VehicleType,VehicleType[0]); 
         switch (typeVehicle) 
          {case "Car" : if (minute <0) 
               {minute = minute +60; 
               hour = hour - 1; 
               double calcalateDuration = hour + (minute/60); 
               double fee = calcalateDuration; 
               String show = "Parking fee: "+fee; 
               JOptionPane.showMessageDialog(null,show,"Vehicle Parking System",JOptionPane.INFORMATION_MESSAGE); 
               JOptionPane.showMessageDialog(null,"Please take your receipt.","Vehicle Parking System",JOptionPane.INFORMATION_MESSAGE); 
               String receipt = "In time: "+inhourInput+" "+inminuteInput+ 
                    "\nOut time: "+outhourInput+" "+inminuteInput+ 
                    "\nDuration: "+hour+"hours and "+minute+"minutes."+ 
                    "\nVehicle Type: "+typeVehicle+ 
                    "\nParking fee: "+fee; 
               JOptionPane.showMessageDialog(null,receipt,"Vehicle Parking System - Parking Receipt",JOptionPane.INFORMATION_MESSAGE);} 
              else 
               {double calcalateDuration = hour + (minute/60); 
               double fee = calcalateDuration; 
               String show = "Parking fee: "+fee; 
               JOptionPane.showMessageDialog(null,show,"Vehicle Parking System",JOptionPane.INFORMATION_MESSAGE); 
               JOptionPane.showMessageDialog(null,"Please take your receipt.","Vehicle Parking System",JOptionPane.INFORMATION_MESSAGE); 
               String receipt = "In time: "+inhourInput+" "+inminuteInput+ 
                    "\nOut time: "+outhourInput+" "+inminuteInput+ 
                    "\nDuration: "+hour+"hours and "+minute+"minutes."+ 
                    "\nVehicle Type: "+typeVehicle+ 
                    "\nParking fee: "+fee; 
               JOptionPane.showMessageDialog(null,receipt,"Vehicle Parking System - Parking Receipt",JOptionPane.INFORMATION_MESSAGE);} 
              break; 

          case "Van" : if (minute <0) 
               {minute = minute +60; 
               hour = hour - 1; 
               double calcalateDuration = hour + (minute/60); 
               double fee = calcalateDuration*120/100; 
               String show = "Parking fee: "+fee; 
               JOptionPane.showMessageDialog(null,show,"Vehicle Parking System",JOptionPane.INFORMATION_MESSAGE); 
               JOptionPane.showMessageDialog(null,"Please take your receipt.","Vehicle Parking System",JOptionPane.INFORMATION_MESSAGE); 
               String receipt = "In time: "+inhourInput+" "+inminuteInput+ 
                    "\nOut time: "+outhourInput+" "+inminuteInput+ 
                    "\nDuration: "+hour+"hours and "+minute+"minutes."+ 
                    "\nVehicle Type: "+typeVehicle+ 
                    "\nParking fee: "+fee; 
               JOptionPane.showMessageDialog(null,receipt,"Vehicle Parking System - Parking Receipt",JOptionPane.INFORMATION_MESSAGE);} 
              else 
               {double calcalateDuration = hour + (minute/60); 
               double fee = calcalateDuration*120/100; 
               String show = "Parking fee: "+fee; 
               JOptionPane.showMessageDialog(null,show,"Vehicle Parking System",JOptionPane.INFORMATION_MESSAGE); 
               JOptionPane.showMessageDialog(null,"Please take your receipt.","Vehicle Parking System",JOptionPane.INFORMATION_MESSAGE); 
               String receipt = "In time: "+inhourInput+" "+inminuteInput+ 
                    "\nOut time: "+outhourInput+" "+inminuteInput+ 
                    "\nDuration: "+hour+"hours and "+minute+"minutes."+ 
                    "\nVehicle Type: "+typeVehicle+ 
                    "\nParking fee: "+fee; 
               JOptionPane.showMessageDialog(null,receipt,"Vehicle Parking System - Parking Receipt",JOptionPane.INFORMATION_MESSAGE);} 
              break; 
          case "Bus" : if (minute <0) 
               {minute = minute +60; 
               hour = hour - 1; 
               double calcalateDuration = hour + (minute/60); 
               double fee = calcalateDuration*140/100; 
               String show = "Parking fee: "+fee; 
               JOptionPane.showMessageDialog(null,show,"Vehicle Parking System",JOptionPane.INFORMATION_MESSAGE); 
               JOptionPane.showMessageDialog(null,"Please take your receipt.","Vehicle Parking System",JOptionPane.INFORMATION_MESSAGE); 
               String receipt = "In time: "+inhourInput+" "+inminuteInput+ 
                    "\nOut time: "+outhourInput+" "+inminuteInput+ 
                    "\nDuration: "+hour+"hours and "+minute+"minutes."+ 
                    "\nVehicle Type: "+typeVehicle+ 
                    "\nParking fee: "+fee; 
               JOptionPane.showMessageDialog(null,receipt,"Vehicle Parking System - Parking Receipt",JOptionPane.INFORMATION_MESSAGE);} 
              else 
               {double calcalateDuration = hour + (minute/60); 
               double fee = calcalateDuration*140/100; 
               String show = "Parking fee: "+fee; 
               JOptionPane.showMessageDialog(null,show,"Vehicle Parking System",JOptionPane.INFORMATION_MESSAGE); 
               JOptionPane.showMessageDialog(null,"Please take your receipt.","Vehicle Parking System",JOptionPane.INFORMATION_MESSAGE); 
               String receipt = "In time: "+inhourInput+" "+inminuteInput+ 
                    "\nOut time: "+outhourInput+" "+inminuteInput+ 
                    "\nDuration: "+hour+"hours and "+minute+"minutes."+ 
                    "\nVehicle Type: "+typeVehicle+ 
                    "\nParking fee: "+fee; 
               JOptionPane.showMessageDialog(null,receipt,"Vehicle Parking System - Parking Receipt",JOptionPane.INFORMATION_MESSAGE);} 
              break; 

          case "Lorry" : if (minute <0) 
               {minute = minute +60; 
               hour = hour - 1; 
               double calcalateDuration = hour + (minute/60); 
               double fee = calcalateDuration*160/100; 
               String show = "Parking fee: "+fee; 
               JOptionPane.showMessageDialog(null,show,"Vehicle Parking System",JOptionPane.INFORMATION_MESSAGE); 
               JOptionPane.showMessageDialog(null,"Please take your receipt.","Vehicle Parking System",JOptionPane.INFORMATION_MESSAGE); 
               String receipt = "In time: "+inhourInput+" "+inminuteInput+ 
                    "\nOut time: "+outhourInput+" "+inminuteInput+ 
                    "\nDuration: "+hour+"hours and "+minute+"minutes."+ 
                    "\nVehicle Type: "+typeVehicle+ 
                    "\nParking fee: "+fee; 
               JOptionPane.showMessageDialog(null,receipt,"Vehicle Parking System - Parking Receipt",JOptionPane.INFORMATION_MESSAGE);} 
              else 
               {double calcalateDuration = hour + (minute/60); 
               double fee = calcalateDuration*160/100; 
               String show = "Parking fee: "+fee; 
               JOptionPane.showMessageDialog(null,show,"Vehicle Parking System",JOptionPane.INFORMATION_MESSAGE); 
               JOptionPane.showMessageDialog(null,"Please take your receipt.","Vehicle Parking System",JOptionPane.INFORMATION_MESSAGE); 
               String receipt = "In time: "+inhourInput+" "+inminuteInput+ 
                    "\nOut time: "+outhourInput+" "+inminuteInput+ 
                    "\nDuration: "+hour+"hours and "+minute+"minutes."+ 
                    "\nVehicle Type: "+typeVehicle+ 
                    "\nParking fee: "+fee; 
               JOptionPane.showMessageDialog(null,receipt,"Vehicle Parking System - Parking Receipt",JOptionPane.INFORMATION_MESSAGE);} 
              break; 
          default  : JOptionPane.showMessageDialog(null,"Unknown Error Occurred!","Vehicle Parking System",JOptionPane.ERROR_MESSAGE); 
              break;}} 


        else 
         JOptionPane.showMessageDialog(null,"Process Canceled.","Vehicle Parking System",JOptionPane.INFORMATION_MESSAGE);} 
      else 
       JOptionPane.showMessageDialog(null,"Process Canceled.","Vehicle Parking System",JOptionPane.INFORMATION_MESSAGE); 



    } 
} 

私は何人かの人々のためにそうでないかもしれない十分な長さ、半日ここでstuckedてきました。しかし、私は本当に助けが必要です。ありがとう。最初の例で

Answer 1

、問題を引き起こしている線は表示されます

double outhourInput = Double.valueOf(outhour); 

参照例外トレースはouthourがNULL /空であることを示しています。したがって、変換する前に、時間が空であるかどうかを確認してください（例：outhour != null && ! outhour.trim().isEmpty()）。

コードを（2番目の例のように）IDEにコピーすると、どこに問題があるのか​​がすぐに分かります。 にはNumberFormatExceptionの問題がありますそれ自体はです。問題は、複数の場所にあり、変数の範囲の問題です。

 if (choice == JOptionPane.OK_OPTION) { 
     try { 
      String inhour = inh.getText(); //-->inhour defined here 
      double inhourInput = Double.valueOf(inhour); 
     } 
     catch (NumberFormatException e) { 
      if (inhour == null || inhour.equals("")) { //-->no scope for inhour 
       inhourInput = 0.0; 
      } 
      else { 
       inhourInput = 0.0; 
      } 
     } 

すべてのブロックで、定義された変数がキャッチブロック内の有効範囲内にあることを確認する必要があります。しかし、いずれの場合も、変数はすべて0.0に設定されているため、ifテストのポイントは表示されません。ただ、明確にすることが

double inhourInput = 0.0; 
String inhour = inh.getText(); 
try { 
    inhour = inh.getText(); 
    inhourInput = Double.valueOf(inhour); 
} 
catch (NumberFormatException e) { 
    // do not really need to reset to 0, but can be useful for clarity 
    inhoutInput = 0.0; 
}