Look for idea.

[Hui Zhao]

Hi, I am going to read a data file to plot a graph.I follow the steps as:
1) choose file, then return file name.

import java.awt.event.*;
import javax.swing.*;
import java.io.*;
import java.io.File;
 
public class FileSelection extends JPanel
{        
  public File getFile() 
  {
        // display file dialog, so user can choose file to open
        final JFileChooser fileChooser = new JFileChooser();
        fileChooser.setFileSelectionMode(JFileChooser.FILES_AND_DIRECTORIES);
        int result = fileChooser.showOpenDialog(this);
        // if user clicked Cancel button on dialog, return
        if( result == JFileChooser.CANCEL_OPTION)
            System.exit(1);
        File fileName = fileChooser.getSelectedFile(); // get selected file
        // display error if invalid
        if ((fileName == null) || (fileName.getName().equals("")))
        {
            JOptionPane.showMessageDialog(this,"Invalid File Name", "Invalid File Name",JOptionPane.ERROR_MESSAGE);
            System.exit(1);
        }
        return fileName;
    }
}

2)to process data by calling the file created in step 1 in another class

public class TestCell 
{    private double ...;
    
    String e[];
    RandomAccessFile file;
    BinaryFile bin;
    public void cellNumber() {
    try
    {
      FileSelection fs = new FileSelection();
      File fileName = fs.getFile();
      file = new RandomAccessFile(fileName, "r");
      DataInputStream in = new DataInputStream(new FileInputStream(fileName));

3)drawing in an applet.

public class Combox extends JApplet
{
private Drawing drawing;
        public void init() {
        try {
            java.awt.EventQueue.invokeAndWait(new Runnable() {
                public void run() {
                    initComponents();
                }
            });
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }
   ...
  private void initComponents() {
    drawing = new Drawing();
    ...
  }
 class Drawing extends JPanel 
{
...
}
    

My question is after I select the file, click ok.Then machine dies and the file chooser dialog is still there. What is wrong with my logic?
Thanks

[Hui Zhao]

please delete the duplicated post, sorry for the pressing Enter mistakenly.

[Bert Bates]

Hi Hui,

Generally it's best to continue with the same thread as opposed to starting a new one with the same question. For instance, in this case you could have simply edited your original post, or added a second post to clarify the question you had. That's for next time, everything is fine for now

[Hui Zhao]

let me reclarify my question to make it understandable.
I am going to select a file by JFileChooser, then return file or file name. but no return at all unless I click the x icon on debug console .
This is an executable code.
Thanks

import java.awt.event.*;
import javax.swing.*;
import java.io.*;
import java.io.File;
 
public class FileSelection 
{        
  public File getFile() 
  {
        // display file dialog, so user can choose file to open
        final JFileChooser fileChooser = new JFileChooser();
        fileChooser.setFileSelectionMode(JFileChooser.FILES_AND_DIRECTORIES);
        JFrame frame = new JFrame();
        int result = fileChooser.showOpenDialog(frame);
        // if user clicked Cancel button on dialog, return
        if( result == JFileChooser.CANCEL_OPTION)
            System.exit(1);
        File fileName = fileChooser.getSelectedFile(); // get selected file
        // display error if invalid
        if ((fileName == null) || (fileName.getName().equals("")))
        {
            JOptionPane.showMessageDialog(frame,"Invalid File Name", "Invalid File Name",JOptionPane.ERROR_MESSAGE);
            System.exit(1);
        }
        return fileName;
    }
}

import java.io.*;
import javax.swing.JFrame;
 
public class FileDemo
{
    public static void main(String args[])
    {
        FileSelection c = new FileSelection();
        
        File name = c.getFile();
        if(name.exists())
            System.out.println("Hello you are lucky");
        else
            System.out.println("Sorry, retry!");
    }
}