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我很難玩餘弦函數。就整數數據類型函數而言，其餘的代碼工作正常，但我不明白爲什麼編譯器會給出雙數據類型函數的錯誤。線程「AWT-EventQueue-0」中的異常java.lang.NumberFormatException：對於輸入字符串「」
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import java.awt.Container;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.text.NumberFormat;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;
/**
*
* @author amjad
*/
public class CalculatorVisual extends JFrame implements ActionListener {
//Methods will be used from this class
CalculatorProps cp = new CalculatorProps();
JTextField val1, val2;
JButton btnPlus, btnMinus, btnMultiply, btnDiv, btnSine, btnCosine, btnTan,
btnPow, btnSqrt, btnModulo, btnLog;
public CalculatorVisual(){
super("Calculator - Visual");
Container c = getContentPane();
val1 = new JTextField(20);
val2 = new JTextField(20);
btnPlus = new JButton("+");
btnMinus = new JButton("-");
btnMultiply = new JButton("X");
btnDiv = new JButton("/");
btnCosine = new JButton("Cos");
btnPlus.addActionListener(this);
btnMinus.addActionListener(this);
btnMultiply.addActionListener(this);
btnDiv.addActionListener(this);
btnCosine.addActionListener(this);
JPanel p = new JPanel();
p.add(val1);
p.add(val2);
p.add(btnPlus);
p.add(btnMinus);
p.add(btnMultiply);
p.add(btnDiv);
p.add(btnCosine);
c.add(p);
}
@Override
public void actionPerformed(ActionEvent e) {
int a = Integer.parseInt(val1.getText());
int b = Integer.parseInt(val2.getText());
if(e.getSource()== btnPlus){
val1.setText("" + cp.sum(a, b));
val2.setText("");
}
else if(e.getSource()== btnMinus){
val1.setText("" + cp.sub(a, b));
val2.setText("");
}
else if(e.getSource() == btnMultiply){
val1.setText("" + cp.multiply(a, b));
val2.setText("");
}
else if(e.getSource() == btnDiv){
val1.setText("" + cp.divide(a, b));
val2.setText("");
}
else if(e.getSource() == btnCosine){
double txtDouble = (double)a;
double d_result = cp.calcCos(txtDouble);
val1.setText(Double.toString(d_result));
val2.setText("");
}
}
public static void main(String[] args) {
CalculatorVisual calc = new CalculatorVisual();
calc.setSize(300,300);
calc.setVisible(true);
calc.setDefaultCloseOperation(3);
}
}
這裏是堆棧跟蹤
Exception in thread "AWT-EventQueue-0" java.lang.NumberFormatException: For input string: ""
at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
at java.lang.Integer.parseInt(Integer.java:592)
at java.lang.Integer.parseInt(Integer.java:615)
at CalculatorVisual.actionPerformed(CalculatorVisual.java:68)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2022)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2346)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
at java.awt.Component.processMouseEvent(Component.java:6525)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3321)
at java.awt.Component.processEvent(Component.java:6290)
at java.awt.Container.processEvent(Container.java:2234)
at java.awt.Component.dispatchEventImpl(Component.java:4881)
at java.awt.Container.dispatchEventImpl(Container.java:2292)
at java.awt.Component.dispatchEvent(Component.java:4703)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4898)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4533)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4462)
at java.awt.Container.dispatchEventImpl(Container.java:2278)
at java.awt.Window.dispatchEventImpl(Window.java:2739)
at java.awt.Component.dispatchEvent(Component.java:4703)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:746)
at java.awt.EventQueue.access$400(EventQueue.java:97)
at java.awt.EventQueue$3.run(EventQueue.java:697)
at java.awt.EventQueue$3.run(EventQueue.java:691)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:75)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:86)
at java.awt.EventQueue$4.run(EventQueue.java:719)
at java.awt.EventQueue$4.run(EventQueue.java:717)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:75)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:716)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)
Exception in thread "AWT-EventQueue-0" java.lang.NumberFormatException: For input string: ""
at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
at java.lang.Integer.parseInt(Integer.java:592)
at java.lang.Integer.parseInt(Integer.java:615)
at CalculatorVisual.actionPerformed(CalculatorVisual.java:68)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2022)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2346)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
at java.awt.Component.processMouseEvent(Component.java:6525)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3321)
at java.awt.Component.processEvent(Component.java:6290)
at java.awt.Container.processEvent(Container.java:2234)
at java.awt.Component.dispatchEventImpl(Component.java:4881)
at java.awt.Container.dispatchEventImpl(Container.java:2292)
at java.awt.Component.dispatchEvent(Component.java:4703)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4898)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4533)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4462)
at java.awt.Container.dispatchEventImpl(Container.java:2278)
at java.awt.Window.dispatchEventImpl(Window.java:2739)
at java.awt.Component.dispatchEvent(Component.java:4703)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:746)
at java.awt.EventQueue.access$400(EventQueue.java:97)
at java.awt.EventQueue$3.run(EventQueue.java:697)
at java.awt.EventQueue$3.run(EventQueue.java:691)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:75)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:86)
at java.awt.EventQueue$4.run(EventQueue.java:719)
at java.awt.EventQueue$4.run(EventQueue.java:717)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:75)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:716)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)
這裏是功能類。我正在使用CalculatorVisual類。
public class CalculatorProps {
int val1,val2, int_result;
double d_val1, d_val2, d_result;
CalculatorProps(){
}
public int sum(int val1,int val2)
{
return int_result = val1+val2;
}
public int sub(int val1,int val2){
return int_result = val1-val2;
}
public int multiply(int val1,int val2){
return int_result = val1*val2;
}
public int divide(int val1,int val2){
return int_result = val1/val2;
}
public int remainder(int val1,int val2){
return int_result = val1 % val2;
}
double sqrt(double d_val1){
double d_result=Math.sqrt(d_val1);
return d_result;
}
double pow(double d_val1,double d_val2){
double d_result=Math.pow(d_val1,d_val2);
return d_result;
}
int fact(int val1){
if(val1<=1)
return 1;
else
return (val1*fact(val1-1));
}
public double calcSine(double d_val1){
double d_result= Math.sin(d_val1);
return d_result;
}
public double calcCos(double d_val1){
double d_result = Math.cos(d_val1);
return d_result;
}
public double calcTan(double d_val1){
double radians = Math.toRadians(d_val1);
return d_result = Math.tan(radians);
}
public double calcLog(double d_val1){
double d_result = Math.log(d_val1);
return d_result;
}
}
一旦我在actionPerformed方法的開頭註釋了val1和val2，它就給了我期望的結果。非常感謝您的回答！所以建議我在開始時或者在actionPerformed中的if/else塊中使用更好的getText方法？ – Amjad 2014-09-25 17:18:07