堆栈内存溢出
  简体   繁体   English

在Java中，如何写入我最近读取的文件？

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

 原文  2012-06-19 13:33:18  0   3    java/ file-io/ text-files

问题描述

I am creating a notepad-type program. 我正在创建一个记事本类型的程序。 Here are my methods to read and write from a file: 以下是我从文件中读取和写入的方法： 

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 和 

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. 当我尝试保存到我之前打开的文件时，我收到Error o1和FileNotFoundException 。

Full Error: 完全错误： 

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)

3 个解决方案

解决方案1
 1  2016-07-15 11:57:28

"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." “FileChannel的Java 5.0文档声明”缓冲区及其表示的映射将保持有效，直到缓冲区本身被垃圾收集“。当我们尝试重新打开文件存储并且映射的字节缓冲区没有时，会发生错误因为没有用于映射字节缓冲区的unmap（）方法（参见bug 4724038），所以当缓冲区空闲时，我们将受到底层操作系统的支配。在Solaris上不会出现问题;可能由于在Solaris上实现共享内存的方式。因此Windows的解决方法是不使用内存映射文件作为事务信息表。“

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

解决方案2
 0  2012-06-19 14:01:39

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." ). 该错误表示您无法写入已被应用程序打开和阻止的文件（有关更多信息： System.IO.Exception错误：“无法对打开了用户映射部分的文件执行请求的操作。 ）。 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. 我认为您必须使用缓冲区，当用户按下按钮保存您直接写入文件时，此外您可以不断检查文件以检查其他用户或应用程序是否已进行更改以通知用户您的应用程序。

If you need an example you can see the Stylepad application, this comes with your JDK installation and usually is installed in 如果您需要一个示例，您可以看到Stylepad应用程序，它随JDK安装一起提供，通常安装在

C:\\Program Files\\Java\\jdk1.6.0_31\\demo\\jfc\\Stylepad 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. 源代码位于文件夹src中，您可以在Stylepad.jar文件中双击执行应用程序。

解决方案3
 0  2013-10-20 21:06:32

This is how you do it. 这就是你如何做到的。 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. 确保将文本文件放在src文件夹和bin文件夹所在的同一文件夹中。（我使用eclipse）如果你想让它在bin文件夹中，那么你需要使文本文件相对。 

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();
        }
    }
}

暂无
暂无

声明:本站的技术帖子网页，遵循CC BY-SA 4.0协议，如果您需要转载，请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.

相关问题 如何从Java中的ArrayLists读取和写入文件 - How do I read and write a file from ArrayLists in Java 如何使用Java中的线程读写文件？ - How do I read and write to a file using threads in java? Java如何读取和写入内部属性文件？ - Java How do I read and write an internal properties file? 如何从Java中的外部进程读取和写入？ - How do I read and write from an external process in Java? 如何在Java中读取/写入文件中的位？ - How can I read/write bits from/to a file in Java? 如何从.txt转换为.xls文件读/写？ - How do I convert from .txt to .xls file read/write? 如何在文件中读写对象的数组列表的数组列表？ - How do I Read/Write an ArrayList of Arraylists of Objects to/from a file? 如何从输入的文件中读取行，然后将最近读取的行存储在数组中？ - How can I read lines from a inputted file and then store the most recently read lines in an array? 如何从 Java jar 文件中读取资源文件？ - How do I read a resource file from a Java jar file? 如何将printStackTrace（）中的异常写入Java中的文本文件？ - How do I write the exception from printStackTrace() into a text file in Java?
相关标签
 
粤ICP备18138465号  © 2020-2024 STACKOOM.COM