In Java, how do I write to a file I recently read from?

Question

I am creating a notepad-type program. Here are my methods to read and write from a file:

BufferedWriter out = null;
try {

    System.out.println("Saving to " + saveFile.getName());
    out = new BufferedWriter(new FileWriter(saveFile));
    out.write(box.getText());

} catch (IOException ex) {
    Logger.getLogger(INoteView.class.getName()).log(Level.SEVERE, null, ex);
    setStatus("ERROR o1");
} finally {
    try {
        out.close();
    } catch (IOException ex) {
        Logger.getLogger(INoteView.class.getName()).log(Level.SEVERE, null, ex);
        setStatus("ERROR o2");
    }
}

and

private static String readFile(File f) throws IOException {
    FileInputStream stream = new FileInputStream(f);
    try {
        FileChannel fc = stream.getChannel();
        MappedByteBuffer bb = fc.map(FileChannel.MapMode.READ_ONLY, 0, fc.size());
        /* Instead of using default, pass in a decoder. */
        return Charset.defaultCharset().decode(bb).toString();
    } finally {
        stream.close();
    }
}

I get the Error o1 and a FileNotFoundException when I try to save to a file I had previously opened.

Full Error:

Jun 19, 2012 9:27:34 AM inote.INoteView jButton2ActionPerformed
SEVERE: null
java.io.FileNotFoundException: D:\My Documents\1.txt (The requested operation cannot be performed on a file with a user-mapped section open)
    at java.io.FileOutputStream.open(Native Method)
    at java.io.FileOutputStream.<init>(FileOutputStream.java:212)
    at java.io.FileOutputStream.<init>(FileOutputStream.java:165)
    at java.io.FileWriter.<init>(FileWriter.java:90)
    at inote.INoteView.jButton2ActionPerformed(INoteView.java:324)
    at inote.INoteView.access$500(INoteView.java:41)
    at inote.INoteView$5.actionPerformed(INoteView.java:173)
    at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
    at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
    at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
    at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
    at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
    at java.awt.Component.processMouseEvent(Component.java:6504)
    at javax.swing.JComponent.processMouseEvent(JComponent.java:3321)
    at java.awt.Component.processEvent(Component.java:6269)
    at java.awt.Container.processEvent(Container.java:2229)
    at java.awt.Component.dispatchEventImpl(Component.java:4860)
    at java.awt.Container.dispatchEventImpl(Container.java:2287)
    at java.awt.Component.dispatchEvent(Component.java:4686)
    at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
    at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
    at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
    at java.awt.Container.dispatchEventImpl(Container.java:2273)
    at java.awt.Window.dispatchEventImpl(Window.java:2713)
    at java.awt.Component.dispatchEvent(Component.java:4686)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:707)
    at java.awt.EventQueue.access$000(EventQueue.java:101)
    at java.awt.EventQueue$3.run(EventQueue.java:666)
    at java.awt.EventQueue$3.run(EventQueue.java:664)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
    at java.awt.EventQueue$4.run(EventQueue.java:680)
    at java.awt.EventQueue$4.run(EventQueue.java:678)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:677)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:211)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:128)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:117)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:113)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:105)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:90)

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at inote.INoteView.jButton2ActionPerformed(INoteView.java:332)
    at inote.INoteView.access$500(INoteView.java:41)
    at inote.INoteView$5.actionPerformed(INoteView.java:173)
    at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
    at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
    at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
    at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
    at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
    at java.awt.Component.processMouseEvent(Component.java:6504)
    at javax.swing.JComponent.processMouseEvent(JComponent.java:3321)
    at java.awt.Component.processEvent(Component.java:6269)
    at java.awt.Container.processEvent(Container.java:2229)
    at java.awt.Component.dispatchEventImpl(Component.java:4860)
    at java.awt.Container.dispatchEventImpl(Container.java:2287)
    at java.awt.Component.dispatchEvent(Component.java:4686)
    at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
    at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
    at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
    at java.awt.Container.dispatchEventImpl(Container.java:2273)
    at java.awt.Window.dispatchEventImpl(Window.java:2713)
    at java.awt.Component.dispatchEvent(Component.java:4686)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:707)
    at java.awt.EventQueue.access$000(EventQueue.java:101)
    at java.awt.EventQueue$3.run(EventQueue.java:666)
    at java.awt.EventQueue$3.run(EventQueue.java:664)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
    at java.awt.EventQueue$4.run(EventQueue.java:680)
    at java.awt.EventQueue$4.run(EventQueue.java:678)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:677)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:211)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:128)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:117)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:113)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:105)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:90)
Saving to 1.txt
Jun 19, 2012 9:28:04 AM inote.INoteView jButton2ActionPerformed
SEVERE: null
java.io.FileNotFoundException: D:\My Documents\1.txt (The requested operation cannot be performed on a file with a user-mapped section open)
    at java.io.FileOutputStream.open(Native Method)
    at java.io.FileOutputStream.<init>(FileOutputStream.java:212)
    at java.io.FileOutputStream.<init>(FileOutputStream.java:165)
    at java.io.FileWriter.<init>(FileWriter.java:90)
    at inote.INoteView.jButton2ActionPerformed(INoteView.java:324)
    at inote.INoteView.access$500(INoteView.java:41)
    at inote.INoteView$5.actionPerformed(INoteView.java:173)
    at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
    at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
    at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
    at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
    at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
    at java.awt.Component.processMouseEvent(Component.java:6504)
    at javax.swing.JComponent.processMouseEvent(JComponent.java:3321)
    at java.awt.Component.processEvent(Component.java:6269)
    at java.awt.Container.processEvent(Container.java:2229)
    at java.awt.Component.dispatchEventImpl(Component.java:4860)
    at java.awt.Container.dispatchEventImpl(Container.java:2287)
    at java.awt.Component.dispatchEvent(Component.java:4686)
    at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
    at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
    at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
    at java.awt.Container.dispatchEventImpl(Container.java:2273)
    at java.awt.Window.dispatchEventImpl(Window.java:2713)
    at java.awt.Component.dispatchEvent(Component.java:4686)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:707)
    at java.awt.EventQueue.access$000(EventQueue.java:101)
    at java.awt.EventQueue$3.run(EventQueue.java:666)
    at java.awt.EventQueue$3.run(EventQueue.java:664)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
    at java.awt.EventQueue$4.run(EventQueue.java:680)
    at java.awt.EventQueue$4.run(EventQueue.java:678)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:677)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:211)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:128)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:117)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:113)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:105)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:90)

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at inote.INoteView.jButton2ActionPerformed(INoteView.java:332)
    at inote.INoteView.access$500(INoteView.java:41)
    at inote.INoteView$5.actionPerformed(INoteView.java:173)
    at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
    at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
    at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
    at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
    at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
    at java.awt.Component.processMouseEvent(Component.java:6504)
    at javax.swing.JComponent.processMouseEvent(JComponent.java:3321)
    at java.awt.Component.processEvent(Component.java:6269)
    at java.awt.Container.processEvent(Container.java:2229)
    at java.awt.Component.dispatchEventImpl(Component.java:4860)
    at java.awt.Container.dispatchEventImpl(Container.java:2287)
    at java.awt.Component.dispatchEvent(Component.java:4686)
    at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
    at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
    at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
    at java.awt.Container.dispatchEventImpl(Container.java:2273)
    at java.awt.Window.dispatchEventImpl(Window.java:2713)
    at java.awt.Component.dispatchEvent(Component.java:4686)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:707)
    at java.awt.EventQueue.access$000(EventQueue.java:101)
    at java.awt.EventQueue$3.run(EventQueue.java:666)
    at java.awt.EventQueue$3.run(EventQueue.java:664)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
    at java.awt.EventQueue$4.run(EventQueue.java:680)
    at java.awt.EventQueue$4.run(EventQueue.java:678)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:677)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:211)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:128)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:117)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:113)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:105)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:90)
BUILD SUCCESSFUL (total time: 1 minute 18 seconds)

Duplicate of http://stackoverflow.com/questions/2972986/how-to-unmap-a-file-from-memory-mapped-using-filechannel-in-java - short answer is that you have to wait for the buffer to be garbage collected, and there's no definitive way to force that. — Ina, Jun 19 '12 at 14:02
@Ina It is similar, but not a duplicate. The other question uses `FileChannel`, which is different from the approach described here. — gobernador, Jun 19 '12 at 14:10
Really? From the OP's source code... `FileChannel fc = stream.getChannel();` — Ina, Jun 19 '12 at 14:31

score 1 · Answer 1 · answered Jul 15 '16 at 11:57

"The Java 5.0 doc for FileChannel state that "the buffer and the mapping that it represents will remain valid until the buffer itself is garbage-collected". The error occurs when we tried to re-open the filestore and the mapped byte buffer has not been GC. Since there is no unmap() method for mapped byte buffer (see bug 4724038), we're at the mercy of the underlying operating system on when the buffer get free up. The problem doesn't occurs on Solaris; may be due to the way shared memory is implemented on Solaris. So the work-around for Windows is not to use memory-mapped file for the transaction information tables."

https://answers.yahoo.com/question/index?qid=20090927164148AAOdJmE

score 0 · Answer 2 · edited May 23 '17 at 11:45

0

The error says that you can't write on a file that is already open and blocked by your application (for more information: System.IO.Exception error: "The requested operation cannot be performed on a file with a user-mapped section open."). I think that you must use a Buffer, when the user press the button save you write directly to the file, in addition you can check constantly the file for checking if other user or application has made changes to notify the user of you application.

If you need an example you can see the Stylepad application, this comes with your JDK installation and usually is installed in

C:\Program Files\Java\jdk1.6.0_31\demo\jfc\Stylepad

The source code is in the folder src, and you can execute the application doing double click in the file Stylepad.jar.

edited May 23 '17 at 11:45

Community

1
1

answered Jun 19 '12 at 14:01

Ernesto Campohermoso

7,213
1
40
51

thanks! I guess I need to stop using new FileWriter and intstead create 1 instance and re-use that – Primm Jun 19 '12 at 14:15
No, the error doesn't say that at all. Note that the file channel he read from is *closed.* The error is far more specific. Not an answer. – user207421 Jun 19 '12 at 22:44

score 0 · Answer 3 · answered Oct 20 '13 at 21:06

This is how you do it. Make sure to have the text file in the same folder the src folder and the bin folder are in. (I use eclipse) If you want it to be in the bin folder than you'll need to make the text file relative.

package read;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.UnsupportedEncodingException;

public class read {
    public static void main(String[] args) throws UnsupportedEncodingException{

        //READ

        String line;
        try {
            BufferedReader reader = new BufferedReader(new FileReader("TEST.txt"));
            do{
                line = reader.readLine();
                if(line != null){
                System.out.println(line);
                }
            }
            while(line != null);
        } catch (IOException e) {
            System.out.println("NO FILE IS THERE");
            e.printStackTrace();
        }

        //WRITE

        try {
            BufferedWriter write = new BufferedWriter(new OutputStreamWriter(
                    new FileOutputStream("TEST.txt")));
            write.newLine();
            write.write("HELLO");
            write.close();
        } catch (FileNotFoundException e) {
            System.out.println("NO FILE IS THERE");
            e.printStackTrace();
        } catch (IOException e) {
            System.out.println("Unable To Write");
            e.printStackTrace();
        }
    }
}

to avoid some close() problems why don't you use try-with-ressources — , Jun 29 '15 at 14:29

In Java, how do I write to a file I recently read from?

3 Answers3