问题：
能源转换器应用程序不起作用，问题可能是在getVal的方法
龚联
请帮我写代码！
问题很可能出在getValues方法上。
每次我输入 2 个值并单击计算按钮时，都会给我很多错误。
我用NetBeans编写了这个程序，这就是为什么代码看起来不像streamlined。
/*
* 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:线程“AWT-event queue-0”Java . lang . numberformatexception:sun . misc . floating decimal . readjavaforomatstring(floating decimal . Java:1011)at Java . lang . float . parse float(float . Java:452)at energy form . get values(energy form . Java:201)at energy form . currentboxactionperform(energy form . Java:182)at energy form . access $ 100(energy form . Java:12
非常感谢帮助！谢了。
共有2个答案
皇甫敏达
你得到一个 NumberFormatException，因为你的 resistanceBox JTextField 是空的。只需为从中读取值的所有字段提供有效的浮点值。您可以在尝试读取值之前添加一个简单的检查，例如：
if (!resistanceBox.getText().trim().isEmpty()) {
resistanceValue = Float.parseFloat(resistanceBox.getText());
} else {
// TODO: alert that R not supplied...
return;
}
请注意，对于欧姆定律，您通常提供2个值来获得第三个值:
V = IR
也可以计算功率:< code>P = VI
由于可以计算电阻R和功率P，因此只能使用电压
柯锋
getValue的前四行都试图将文本字段中的值转换为浮点数。除非所有四个文本字段都有数据，否则这些行中至少有一行会抛出NumberFormatExc的异常。在尝试解析浮点数之前，您应该（1）检查特定文本字段是否为空，并且（2）捕获NumberFormatExceptions来处理用户输入无效数据的情况。
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