java - Energy Converter 应用程序无法工作，问题可能出在 getValues 方法中

Question

请帮我修改我的代码!

问题很可能出现在 getValues 方法中。

每次我输入 2 个值并单击计算按钮时，都会出现很多错误。

我使用 NetBeans 对其进行了编程，这就是代码看起来不精简的原因。

 /*
     * To change this template, choose Tools | Templates
     * and open the template in the editor.
     */

    /**
     *
     * @author cshames
     */
    import java.text.DecimalFormat;
    import java.lang.Math.*;
    public class EnergyForm extends javax.swing.JFrame {
        public static DecimalFormat hundred = new DecimalFormat("0.00");
        public static double voltageValue;
        public static double currentValue;
        public static double resistanceValue;
        public static double powerValue;



        /**
         * Creates new form EnergyForm
         */
        public EnergyForm() {
            initComponents();
        }

        /**
         * This method is called from within the constructor to initialize the form.
         * WARNING: Do NOT modify this code. The content of this method is always
         * regenerated by the Form Editor.
         */
        @SuppressWarnings("unchecked")
        // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
        private void initComponents() {

            voltageBox = new javax.swing.JTextField();
            currentBox = new javax.swing.JTextField();
            resistanceBox = new javax.swing.JTextField();
            powerBox = new javax.swing.JTextField();
            jLabel1 = new javax.swing.JLabel();
            jLabel2 = new javax.swing.JLabel();
            jLabel3 = new javax.swing.JLabel();
            jLabel4 = new javax.swing.JLabel();
            jLabel5 = new javax.swing.JLabel();
            calculateButton = new javax.swing.JButton();
            resetButton = new javax.swing.JButton();

            setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

            voltageBox.addActionListener(new java.awt.event.ActionListener() {
                public void actionPerformed(java.awt.event.ActionEvent evt) {
                    voltageBoxActionPerformed(evt);
                }
            });

            currentBox.addActionListener(new java.awt.event.ActionListener() {
                public void actionPerformed(java.awt.event.ActionEvent evt) {
                    currentBoxActionPerformed(evt);
                }
            });

            resistanceBox.addActionListener(new java.awt.event.ActionListener() {
                public void actionPerformed(java.awt.event.ActionEvent evt) {
                    resistanceBoxActionPerformed(evt);
                }
            });

            powerBox.addActionListener(new java.awt.event.ActionListener() {
                public void actionPerformed(java.awt.event.ActionEvent evt) {
                    powerBoxActionPerformed(evt);
                }
            });

            jLabel1.setText("Voltage:");

            jLabel2.setText("Current:");

            jLabel3.setText("Resistance:");

            jLabel4.setText("Power:");

            jLabel5.setFont(new java.awt.Font("Comic Sans MS", 0, 14)); // NOI18N
            jLabel5.setText("Ohm's Law Converter");

            calculateButton.setText("Calculate");
            calculateButton.addActionListener(new java.awt.event.ActionListener() {
                public void actionPerformed(java.awt.event.ActionEvent evt) {
                    calculateButtonActionPerformed(evt);
                }
            });

            resetButton.setText("Reset");
            resetButton.addActionListener(new java.awt.event.ActionListener() {
                public void actionPerformed(java.awt.event.ActionEvent evt) {
                    resetButtonActionPerformed(evt);
                }
            });

            javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
            getContentPane().setLayout(layout);
            layout.setHorizontalGroup(
                layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                .addGroup(layout.createSequentialGroup()
                    .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING)
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                            .addGroup(layout.createSequentialGroup()
                                .addGap(66, 66, 66)
                                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING)
                                    .addComponent(jLabel3)
                                    .addComponent(jLabel4))
                                .addGap(18, 18, 18)
                                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING, false)
                                    .addComponent(powerBox, javax.swing.GroupLayout.DEFAULT_SIZE, 50, Short.MAX_VALUE)
                                    .addComponent(resistanceBox))
                                .addGap(0, 0, Short.MAX_VALUE))
                            .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
                                .addContainerGap(71, Short.MAX_VALUE)
                                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                                    .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
                                        .addComponent(calculateButton)
                                        .addGap(33, 33, 33)
                                        .addComponent(resetButton))
                                    .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
                                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING)
                                            .addComponent(jLabel1)
                                            .addComponent(jLabel2))
                                        .addGap(18, 18, 18)
                                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                                            .addComponent(currentBox, javax.swing.GroupLayout.PREFERRED_SIZE, 50, javax.swing.GroupLayout.PREFERRED_SIZE)
                                            .addComponent(voltageBox, javax.swing.GroupLayout.PREFERRED_SIZE, 50, javax.swing.GroupLayout.PREFERRED_SIZE))
                                        .addGap(170, 170, 170)))))
                        .addGroup(javax.swing.GroupLayout.Alignment.LEADING, layout.createSequentialGroup()
                            .addGap(98, 98, 98)
                            .addComponent(jLabel5, javax.swing.GroupLayout.PREFERRED_SIZE, 151, javax.swing.GroupLayout.PREFERRED_SIZE)))
                    .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
            );
            layout.setVerticalGroup(
                layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                .addGroup(layout.createSequentialGroup()
                    .addGap(21, 21, 21)
                    .addComponent(jLabel5)
                    .addGap(18, 18, 18)
                    .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                        .addComponent(voltageBox, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addComponent(jLabel1))
                    .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                    .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                        .addComponent(currentBox, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addComponent(jLabel2))
                    .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                    .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                        .addComponent(resistanceBox, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addComponent(jLabel3))
                    .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                    .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                        .addComponent(powerBox, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addComponent(jLabel4))
                    .addGap(18, 18, 18)
                    .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                        .addComponent(resetButton)
                        .addComponent(calculateButton))
                    .addContainerGap(30, Short.MAX_VALUE))
            );

            pack();
        }// </editor-fold>                        

        private void voltageBoxActionPerformed(java.awt.event.ActionEvent evt) {                                           
            getValues();
        }                                          

        private void resistanceBoxActionPerformed(java.awt.event.ActionEvent evt) {                                              
            getValues();
        }                                             

        private void powerBoxActionPerformed(java.awt.event.ActionEvent evt) {                                         
            getValues();
        }                                        

        private void currentBoxActionPerformed(java.awt.event.ActionEvent evt) {                                           
            getValues();
        }                                          

        private void calculateButtonActionPerformed(java.awt.event.ActionEvent evt) {                                                
            getValues();
        }                                               

        private void resetButtonActionPerformed(java.awt.event.ActionEvent evt) {                                            
            powerBox.setText(null);
            voltageBox.setText(null);
            currentBox.setText(null);
            resistanceBox.setText(null);
        }                                           

        /**
         * @param args the command line arguments
         */
//help here please! 
       public static void getValues() {
            voltageValue = Float.parseFloat(voltageBox.getText());
            resistanceValue = Float.parseFloat(resistanceBox.getText());
            currentValue = Float.parseFloat(currentBox.getText());
            powerValue = Float.parseFloat(powerBox.getText());
            //if(current==true&&voltage==true){//finds resistance & power
              if(currentBox.getText() != null && voltageBox.getText() != null) { 
                  resistanceValue=voltageValue/currentValue;
                  powerValue=voltageValue*currentValue;
                  String resistanceValueString = hundred.format(resistanceValue);
                  String powerValueString = hundred.format(powerValue);
                  resistanceBox.setText(resistanceValueString);
                  powerBox.setText(powerValueString);

            }
            else if(currentBox.getText() != null && resistanceBox.getText() != null){//finds voltage & power
                voltageValue=resistanceValue*currentValue;
                powerValue=(currentValue*currentValue)*resistanceValue;
                 String voltageValueString = hundred.format(voltageValue);
                  String powerValueString = hundred.format(powerValue);
                  voltageBox.setText(voltageValueString);
                  powerBox.setText(powerValueString);

            }
            else if(resistanceBox.getText() != null && voltageBox.getText() != null){//finds current & power
                currentValue=voltageValue/resistanceValue;
                powerValue=(voltageValue*voltageValue)/resistanceValue;
                 String currentValueString = hundred.format(currentValue);
                  String powerValueString = hundred.format(powerValue);
                  currentBox.setText(currentValueString);
                  powerBox.setText(powerValueString);

            }
            else if(powerBox.getText() != null && voltageBox.getText() != null){//finds current & resistance
                currentValue=powerValue/voltageValue;
                resistanceValue=(voltageValue*voltageValue)/powerValue;
                 String currentValueString = hundred.format(currentValue);
                  String resistanceValueString = hundred.format(resistanceValue);
                  resistanceBox.setText(resistanceValueString);
                  currentBox.setText(currentValueString);

            }
            else if(currentBox.getText() != null && powerBox.getText() != null){//finds voltage & resistance
                voltageValue=powerValue/currentValue;
                resistanceValue=powerValue/(currentValue*currentValue);
                 String resistanceValueString = hundred.format(resistanceValue);
                  String voltageValueString = hundred.format(voltageValue);
                  resistanceBox.setText(resistanceValueString);
                  voltageBox.setText(voltageValueString);

            }
            else if(resistanceBox.getText() != null && powerBox.getText() != null){//finds voltage & current
                voltageValue=Math.sqrt((powerValue*resistanceValue));
                currentValue=Math.sqrt(powerValue/resistanceValue);    
                 String currentValueString = hundred.format(currentValue);
                  String voltageValueString = hundred.format(voltageValue);
                  currentBox.setText(currentValueString);
                  voltageBox.setText(voltageValueString);
            }

        }
        public static void main(String args[]) {
            /* Set the Nimbus look and feel */
            //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
            /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
             * For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html 
             */
            try {
                for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
                    if ("Nimbus".equals(info.getName())) {
                        javax.swing.UIManager.setLookAndFeel(info.getClassName());
                        break;
                    }
                }
            } catch (ClassNotFoundException ex) {
                java.util.logging.Logger.getLogger(EnergyForm.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
            } catch (InstantiationException ex) {
                java.util.logging.Logger.getLogger(EnergyForm.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
            } catch (IllegalAccessException ex) {
                java.util.logging.Logger.getLogger(EnergyForm.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
            } catch (javax.swing.UnsupportedLookAndFeelException ex) {
                java.util.logging.Logger.getLogger(EnergyForm.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
            }
            //</editor-fold>

            /* Create and display the form */
            java.awt.EventQueue.invokeLater(new Runnable() {
                public void run() {
                    new EnergyForm().setVisible(true);
                }
            });
        }
        // Variables declaration - do not modify                     
        private javax.swing.JButton calculateButton;
        private static javax.swing.JTextField currentBox;
        private javax.swing.JLabel jLabel1;
        private javax.swing.JLabel jLabel2;
        private javax.swing.JLabel jLabel3;
        private javax.swing.JLabel jLabel4;
        private javax.swing.JLabel jLabel5;
        private static javax.swing.JTextField powerBox;
        private javax.swing.JButton resetButton;
        private static javax.swing.JTextField resistanceBox;
        private static javax.swing.JTextField voltageBox;
        // End of variables declaration                   
    }
    /**
     * if(textfield.getText()!=null&&othertextfield.getText()!=null){
     *     
     * }
     */

错误消息:

run: Exception in thread "AWT-EventQueue-0" java.lang.NumberFormatException: empty String at sun.misc.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:1011) at java.lang.Float.parseFloat(Float.java:452) at EnergyForm.getValues(EnergyForm.java:201) at EnergyForm.currentBoxActionPerformed(EnergyForm.java:182) at EnergyForm.access$100(EnergyForm.java:12) at EnergyForm$2.actionPerformed(EnergyForm.java:59) at javax.swing.JTextField.fireActionPerformed(JTextField.java:508) at javax.swing.JTextField.postActionEvent(JTextField.java:721) at javax.swing.JTextField$NotifyAction.actionPerformed(JTextField.java:836) at javax.swing.SwingUtilities.notifyAction(SwingUtilities.java:1664) at javax.swing.JComponent.processKeyBinding(JComponent.java:2879) at javax.swing.JComponent.processKeyBindings(JComponent.java:2926) at javax.swing.JComponent.processKeyEvent(JComponent.java:2842) at java.awt.Component.processEvent(Component.java:6282) at java.awt.Container.processEvent(Container.java:2229) at java.awt.Component.dispatchEventImpl(Component.java:4861) at java.awt.Container.dispatchEventImpl(Container.java:2287) at java.awt.Component.dispatchEvent(Component.java:4687) at java.awt.KeyboardFocusManager.redispatchEvent(KeyboardFocusManager.java:1895) at java.awt.DefaultKeyboardFocusManager.dispatchKeyEvent(DefaultKeyboardFocusManager.java:762) at java.awt.DefaultKeyboardFocusManager.preDispatchKeyEvent(DefaultKeyboardFocusManager.java:1027) at java.awt.DefaultKeyboardFocusManager.typeAheadAssertions(DefaultKeyboardFocusManager.java:899) at java.awt.DefaultKeyboardFocusManager.dispatchEvent(DefaultKeyboardFocusManager.java:727) at java.awt.Component.dispatchEventImpl(Component.java:4731) at java.awt.Container.dispatchEventImpl(Container.java:2287) at java.awt.Window.dispatchEventImpl(Window.java:2719) at java.awt.Component.dispatchEvent(Component.java:4687) at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:729) at java.awt.EventQueue.access$200(EventQueue.java:103) at java.awt.EventQueue$3.run(EventQueue.java:688) at java.awt.EventQueue$3.run(EventQueue.java:686) at java.security.AccessController.doPrivileged(Native Method) at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76) at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87) at java.awt.EventQueue$4.run(EventQueue.java:702) at java.awt.EventQueue$4.run(EventQueue.java:700) at java.security.AccessController.doPrivileged(Native Method) at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76) at java.awt.EventQueue.dispatchEvent(EventQueue.java:699) at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242) at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161) at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138) at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)

非常感谢您的帮助!谢谢。

Answer 1

getValues 的前四行都尝试将文本字段中的值转换为 float 。除非所有四个文本字段都有数据，否则至少其中一行将抛出 NumberFormatException。您应该 (1) 在尝试解析 float 之前检查特定文本字段是否不为空，以及 (2) 捕获 NumberFormatExceptions 以处理用户输入无效数据的情况。