Programming Forums > Application Development > Java

Riddick · Apr 8th, 2007, 2:13 PM

Hi, i'm trying to add a file extension to a file when the user has typed in the filename without an extension (in a JFileChooser). I've managed to recognise that the file is missing an extension.

(Toggle Plain Text)

String extension = null;
String fileName = file.getName();
		
int i = fileName.lastIndexOf('.');
		
if(i > 0 && i < fileName.length() - 1)
{
	extension = fileName.substring(i + 1).toLowerCase();
}

And from here i can work out the required extension from the filefilters but i don't know how to rename the file before i save it. Can anyone help?

titaniumdecoy · Apr 8th, 2007, 5:36 PM

Try the renameTo method of the File class.

Riddick · Apr 9th, 2007, 4:15 AM

Hi thanks. But my understanding of renameTo is that it renames a 'physical' file on disk. However my file object has not necessarily been stored to disk. I.e. it's the first time the filename is being used. Here is my code (some of it). The way i need it to work is, if you try to save the file with no extension then the filename is automatically appended to '.txt'. Thanks.

(Toggle Plain Text)

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.io.*;

public class FileTest
{
	private static JFrame frame = new JFrame();
	private static JPanel panel = new JPanel();
	private static JTextPane txtPane = new JTextPane();
	private static File file = null;
	private static JFileChooser chooser = new JFileChooser();
	private static JButton button = new JButton("Save Me");
	
	public static void main(String[] args)
	{
		panel.setLayout(new BorderLayout());
		frame.setContentPane(panel);
		JScrollPane pane = new JScrollPane(txtPane);
		
		button.addActionListener(new ActionListener()
		{
			public void actionPerformed(ActionEvent e)
			{
				save();
			}
		});
		frame.getContentPane().add(button, BorderLayout.SOUTH);
		
		panel.add(pane);
		frame.setSize(400, 300);
		frame.setVisible(true);		
	}
	
	public static void save()
	{
		int option = chooser.showSaveDialog(frame);
		
		if(option != chooser.APPROVE_OPTION)
			return;
		
		file = chooser.getSelectedFile();
		
		setExt();
		
		FileWriter writer = null;
		
		try
		{
			writer = new FileWriter(file);
			txtPane.write(writer);
		}
		catch(IOException ex){}
		finally
		{
			try{	writer.close();	}
			catch(IOException ioe){}
		}
	}
	
	public static void setExt()
	{
		String ext = null;
		String fileName = file.getName();
		
		int i = fileName.lastIndexOf('.');
		
		if(i > 0 && i < fileName.length() - 1)
		{
			ext = fileName.substring(i + 1).toLowerCase();
			System.out.println(ext);
		}
		else
		{
			fileName = fileName + ".txt";
			boolean renamed = file.renameTo(new File(fileName));

			if(renamed)
				System.out.println("Renamed: " + file.getName());
			else
				System.out.println("Not Renamed: " + file.getName());
		}
	}
}

Riddick · Apr 11th, 2007, 10:22 AM

I've solved it now.

I just appended the parameter in the FileWriter

(Toggle Plain Text)

FileWriter fileWriter = new FileWriter(fileName + ext);

Ooble · Apr 13th, 2007, 7:55 PM

But what if filename is "something.txt"?

(Toggle Plain Text)

if (!filename.substr(filename.length() - 4).equals(ext))
{
    filename += ext;
}

Riddick · Apr 14th, 2007, 12:31 PM

In the actual application the setExtention method returns a null value to a string variable if the file has an extension. Then depending on that variable the file is save with or without an appended extension.

Apr 8th, 2007, 2:13 PM	#1
Riddick Newbie Join Date: Sep 2006 Posts: 14 Rep Power: 0	File extensions Hi, i'm trying to add a file extension to a file when the user has typed in the filename without an extension (in a JFileChooser). I've managed to recognise that the file is missing an extension. (Toggle Plain Text) String extension = null; String fileName = file.getName(); int i = fileName.lastIndexOf('.'); if(i > 0 && i < fileName.length() - 1) { extension = fileName.substring(i + 1).toLowerCase(); } String extension = null; String fileName = file.getName(); int i = fileName.lastIndexOf('.'); if(i > 0 && i < fileName.length() - 1) { extension = fileName.substring(i + 1).toLowerCase(); } And from here i can work out the required extension from the filefilters but i don't know how to rename the file before i save it. Can anyone help?

Apr 9th, 2007, 4:15 AM	#3
Riddick Newbie Join Date: Sep 2006 Posts: 14 Rep Power: 0	Hi thanks. But my understanding of renameTo is that it renames a 'physical' file on disk. However my file object has not necessarily been stored to disk. I.e. it's the first time the filename is being used. Here is my code (some of it). The way i need it to work is, if you try to save the file with no extension then the filename is automatically appended to '.txt'. Thanks. (Toggle Plain Text) import java.awt.; import java.awt.event.; import javax.swing.; import java.io.; public class FileTest { private static JFrame frame = new JFrame(); private static JPanel panel = new JPanel(); private static JTextPane txtPane = new JTextPane(); private static File file = null; private static JFileChooser chooser = new JFileChooser(); private static JButton button = new JButton("Save Me"); public static void main(String[] args) { panel.setLayout(new BorderLayout()); frame.setContentPane(panel); JScrollPane pane = new JScrollPane(txtPane); button.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { save(); } }); frame.getContentPane().add(button, BorderLayout.SOUTH); panel.add(pane); frame.setSize(400, 300); frame.setVisible(true); } public static void save() { int option = chooser.showSaveDialog(frame); if(option != chooser.APPROVE_OPTION) return; file = chooser.getSelectedFile(); setExt(); FileWriter writer = null; try { writer = new FileWriter(file); txtPane.write(writer); } catch(IOException ex){} finally { try{ writer.close(); } catch(IOException ioe){} } } public static void setExt() { String ext = null; String fileName = file.getName(); int i = fileName.lastIndexOf('.'); if(i > 0 && i < fileName.length() - 1) { ext = fileName.substring(i + 1).toLowerCase(); System.out.println(ext); } else { fileName = fileName + ".txt"; boolean renamed = file.renameTo(new File(fileName)); if(renamed) System.out.println("Renamed: " + file.getName()); else System.out.println("Not Renamed: " + file.getName()); } } } import java.awt.; import java.awt.event.; import javax.swing.; import java.io.; public class FileTest { private static JFrame frame = new JFrame(); private static JPanel panel = new JPanel(); private static JTextPane txtPane = new JTextPane(); private static File file = null; private static JFileChooser chooser = new JFileChooser(); private static JButton button = new JButton("Save Me"); public static void main(String[] args) { panel.setLayout(new BorderLayout()); frame.setContentPane(panel); JScrollPane pane = new JScrollPane(txtPane); button.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { save(); } }); frame.getContentPane().add(button, BorderLayout.SOUTH); panel.add(pane); frame.setSize(400, 300); frame.setVisible(true); } public static void save() { int option = chooser.showSaveDialog(frame); if(option != chooser.APPROVE_OPTION) return; file = chooser.getSelectedFile(); setExt(); FileWriter writer = null; try { writer = new FileWriter(file); txtPane.write(writer); } catch(IOException ex){} finally { try{ writer.close(); } catch(IOException ioe){} } } public static void setExt() { String ext = null; String fileName = file.getName(); int i = fileName.lastIndexOf('.'); if(i > 0 && i < fileName.length() - 1) { ext = fileName.substring(i + 1).toLowerCase(); System.out.println(ext); } else { fileName = fileName + ".txt"; boolean renamed = file.renameTo(new File(fileName)); if(renamed) System.out.println("Renamed: " + file.getName()); else System.out.println("Not Renamed: " + file.getName()); } } }

Apr 11th, 2007, 10:22 AM	#4
Riddick Newbie Join Date: Sep 2006 Posts: 14 Rep Power: 0	I've solved it now. I just appended the parameter in the FileWriter (Toggle Plain Text) FileWriter fileWriter = new FileWriter(fileName + ext); FileWriter fileWriter = new FileWriter(fileName + ext);

Apr 13th, 2007, 7:55 PM	#5
Ooble I eat cake for breakfast. Join Date: Jul 2004 Location: In my box. Posts: 4,434 Rep Power: 9	But what if filename is "something.txt"? (Toggle Plain Text) if (!filename.substr(filename.length() - 4).equals(ext)) { filename += ext; } if (!filename.substr(filename.length() - 4).equals(ext)) { filename += ext; } __________________ Me :: You :: Them

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Apr 8th, 2007, 5:36 PM	#2
titaniumdecoy Expert Programmer Join Date: Nov 2005 Posts: 856 Rep Power: 3	Try the renameTo method of the File class.

Apr 14th, 2007, 12:31 PM	#6
Riddick Newbie Join Date: Sep 2006 Posts: 14 Rep Power: 0	In the actual application the setExtention method returns a null value to a string variable if the file has an extension. Then depending on that variable the file is save with or without an appended extension.

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Programming Forums > Application Development > Java

File extensions