FileDescriptor 示例：确保文件保存到磁盘中，filedescriptor示例,import java.

FileDescriptor 示例：确保文件保存到磁盘中，filedescriptor示例,import java.

import java.io.FileOutputStream;import java.io.FileDescriptor;import java.io.IOException;/** * ----------------------------------------------------------------------------- * This program demonstrates how to force updates to a file to a disk. In some * applications, such as transaction processing, it is necessary to ensure that * an update has been made to the disk. FileDescriptor.sunc() blocks until * all changes to a file are written to disk. * * @version 1.0 * @author  Jeffrey M. Hunter  (jhunter@idevelopment.info) * @author  <a href="http://www.idevelopment.info">http://www.idevelopment.info * ----------------------------------------------------------------------------- */public class ForcingUpdates {    private static void doForceUpdate() {        try {            // Open or create the output file            String           fn = "outfile.txt";            FileOutputStream os = new FileOutputStream(fn);            FileDescriptor   fd = os.getFD();            System.out.println("Opened file: " + fn);            // Write some data to the stream            byte[] data = new byte[]{(byte)0xCA, (byte)0xFE, (byte)0xBA, (byte)0xBE};            os.write(data);            System.out.println("Wrote the following data to stream: " + data);            // Flush the data from the streams and writers into system buffers.            // The data may or may not be written to disk.            System.out.println("Flushing from streams to system buffers.");            os.flush();            // Block until the system buffers have been written to disk.            // After this method returns, the data is guaranteed to have been            // written to disk.            System.out.println("Blocking until system buffers have been written.");            fd.sync();            // Close out the file stream            os.close();            System.out.println("Closed file: " + fn);        } catch (IOException e) {            e.printStackTrace();        }    }    /**     * Sole entry point to the class and application.     * @param args Array of String arguments.     */    public static void main(String[] args) {        doForceUpdate();    }}//该片段来自于http://byrx.net