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我一直在運行該程序編譯但運行不正常。當我運行它並嘗試執行計算時，它會吐出一堆錯誤。我認爲它必須與變量類型。這裏是程序：線程「AWT-EventQueue-0」中的異常java.lang.NumberFormatException：空字符串
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();
}
}
這裏是錯誤打印出來時，試圖執行數學（抱歉它真的很長）。在sun.misc.FloatingDecimal.readJavaFormatString（FloatingDecimal.java:1038）
空字符串
在java.lang.Double中：
在異常線程 「AWT-EventQueue的-0」 java.lang.NumberFormatException。 parseDouble（Double.java:548）
在area.actionPerformed（area.java:112）
...
在此先感謝這麼多的幫助！