好的，所以基本上，我的头很痛，我现在被困住了。所以我有一个程序，它有一个打开按钮和一个文本区域。当您使用 hte 打开按钮时，您将打开一个用 Excel 制作的 csv 文件。我的程序应该打开一个文件，将其附加到文本区域，但随后我试图将所有值存储到一个多维数组中，以便我可以使用另一个类来计算诸如最高值和最低值。到目前为止，我刚刚开始尝试做最高的价值，但我没有运气。该文件打开并附加，但最大值出现某种错误。如果有人可以帮助我解决这个问题，我会非常感谢它。
主班
import java.awt.BorderLayout;
import java.awt.EventQueue;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.border.EmptyBorder;
import javax.swing.filechooser.FileNameExtensionFilter;
import javax.swing.JButton;
import javax.swing.JTextField;
import java.awt.TextArea;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
public class task3 extends JFrame {
public static JPanel contentPane;
public JTextField txtOpen;
public JButton btnOpen;
public static TextArea textArea;
int rows = 9, columns = 1441; //Columns up and down, rows across. Number of rows and columns in excell file.
double[][] data = new double[rows][columns]; //Array to hold the rows and columns.
/**
* Launch the application.
*/
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
task3 frame = new task3();
frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
/**
* Create the frame.
*/
public task3() {
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setBounds(100, 100, 560, 350);
contentPane = new JPanel();
contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
setContentPane(contentPane);
contentPane.setLayout(null);
btnOpen = new JButton("Open");
btnOpen.addMouseListener(new MouseAdapter() {
@Override
public void mouseClicked(MouseEvent arg0) {
try{
JFileChooser chooser = new JFileChooser(); //File Chooser
chooser.setFileFilter(new FileNameExtensionFilter("Excell CSV Files", "csv"));
chooser.removeChoosableFileFilter(chooser.getAcceptAllFileFilter()); //Filters for csv file
//Get the file
int returnVal = chooser.showOpenDialog(task3.contentPane);
File file;
if(returnVal == JFileChooser.APPROVE_OPTION) {
file = chooser.getSelectedFile();
}
else{
file = null;
}
//Read the file into variable
BufferedReader in = new BufferedReader(new FileReader(file));
String line = in.readLine();
while(line != null){
task3.textArea.append(line + "\n");
line = in.readLine(); //Print out into text area
}
for(int i = 0; i < rows; i++){
//Use a temporary array to hold the rows in whilst the data is split.
String array [] = line.split(","); //Split the data up using the commas.
for(int j = 0; j < columns; j++){
//Take the rows and columns and convert them into a double so they can be saved into the array.
data[i][j] = Double.parseDouble(array[j]);
}
}
}catch(Exception e){
e.printStackTrace();
}
double max = task3Methods.Max(data);
textArea.append("\n\nmax is: "+max);
}
});
btnOpen.setBounds(256, 22, 89, 23);
contentPane.add(btnOpen);
txtOpen = new JTextField();
txtOpen.setBounds(61, 23, 174, 20);
contentPane.add(txtOpen);
txtOpen.setColumns(10);
textArea = new TextArea();
textArea.setBounds(27, 57, 507, 245);
contentPane.add(textArea);
}
}
方法类
public class task3Methods {
public static double Max(double[][] data){
double temp;
double high = Double.MIN_VALUE; //State this variable hold the largest possible double in the file.
for (int i = 0; i < data.length; i++){ //Loop through the data.
for(int j = 0; j < data[i].length; j++){
temp = data[i][j];
if(temp > high){ //If a number in the array is larger than the current highest value...
high = temp; //Store the new highest value.
}
}
}
return high;
}
}
这是我在下拉框中使用的 Excel 文件的链接 https://www.dropbox.com/s/62ssjoph2z6vmv3/Temperature_Log.csv
对不起，这是确切的错误
java.lang.NullPointerException
at task3$2.mouseClicked(task3.java:86)
at java.awt.AWTEventMulticaster.mouseClicked(Unknown Source)
at java.awt.Component.processMouseEvent(Unknown Source)
at javax.swing.JComponent.processMouseEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$200(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)
在文本区域中，不是说 Max = 21.5456 或其他什么，而是说 max is: 4.9E-324