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[英]Exception in thread “AWT-EventQueue-0” java.lang.NumberFormatException: empty
[英]Exception in thread “AWT-EventQueue-0” java.lang.NumberFormatException: empty String
我在運行該程序時遇到了問題,該程序可以編譯但無法正常運行。 當我運行它並嘗試執行計算時,它會吐出一堆錯誤。 我認為它必須與變量類型有關。 這是程序:
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class area extends JFrame implements ActionListener, ItemListener{
//row 1
JPanel row1 = new JPanel();
JLabel select = new JLabel("Please select what you would like to caculate the area and volume of.");
//row 2
JPanel row2 = new JPanel();
JCheckBox circle = new JCheckBox("Circle", false);
JCheckBox cube = new JCheckBox("Cube", false);
//row 3
JPanel row3 = new JPanel();
JLabel radlab = new JLabel("Radius of the circle (in cm)");
JTextField rad = new JTextField(3);
JLabel sidelab = new JLabel("A side of the cube (in cm)");
JTextField side = new JTextField(3);
//row4
JPanel row4 = new JPanel();
JButton solve = new JButton("Solve!");
//row 5
JPanel row5 = new JPanel();
JLabel areacallab = new JLabel("Area");
JTextField areacal = new JTextField(10);
JLabel volumelab = new JLabel("Volume");
JTextField volume = new JTextField(10);
public area(){
setTitle("Area Caculator");
setSize(500,400);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setVisible(true);
//disables all text areas
rad.setEnabled(false);
side.setEnabled(false);
areacal.setEnabled(false);
volume.setEnabled(false);
//add listeners
circle.addItemListener(this);
cube.addItemListener(this);
solve.addActionListener(this);
FlowLayout one = new FlowLayout(FlowLayout.CENTER);
setLayout(one);
row1.add(select);
add(row1);
row2.add(circle);
row2.add(cube);
add(row2);
row3.add(radlab);
row3.add(rad);
row3.add(sidelab);
row3.add(side);
add(row3);
row4.add(solve);
add(row4);
row5.add(areacallab);
row5.add(areacal);
row5.add(volumelab);
row5.add(volume);
add(row5);
}
public void circlepick(){
//cube.setCurrent(false);
cube.setEnabled(false);
rad.setEnabled(true);
}
public void cubepick(){
circle.setEnabled(false);
side.setEnabled(true);
}
@Override
public void itemStateChanged(ItemEvent event) {
Object item = event.getItem();
if (item == circle){
circlepick();
}
else if (item == cube){
cubepick();
}
}
@Override
public void actionPerformed(ActionEvent evt){
//String radi = rad.getText();
//String sid = side.getText();
//circlesolve();
//cubesolve();
String radi = rad.getText();
String sid = side.getText();
double radius = Double.parseDouble(radi);
double length = Double.parseDouble(sid);
double cirarea = Math.PI * Math.pow(radius, 2);
double cirvolume = (4.0 / 3) * Math.PI * Math.pow(radius, 3);
double cubearea = Math.pow(length, 2);
double cubevolume = Math.pow(length, 3);
areacal.setText("" + cirarea + cubearea + "");
volume.setText("" + cirvolume + cubevolume + "");
}
public static void main(String[] args) {
area are = new area();
}
}
這是嘗試執行數學運算時打印出來的錯誤(很長一段時間對不起)。
線程“ AWT-EventQueue-0”中的異常java.lang.NumberFormatException:空字符串
在sun.misc.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:1038)
在java.lang.Double.parseDouble(Double.java:548)
在area.actionPerformed(area.java:112)
...
非常感謝您的幫助!
調用函數時:
double radius = Double.parseDouble(radi);
double length = Double.parseDouble(sid);
radi
或sid
是Empty String
,這就是
java.lang.NumberFormatException: empty String
告訴你。
您可以在解析之前考慮添加System.out.println(raid + ", " + sid)
,以檢查哪些值是空字符串,並確保該字符串不為空。
當無法將給定的String s
解析為double
值時, Double.parseDouble(String s)
引發NumberFormatException
。
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