用FileChannel拷贝文件

 用filechannel更方便一些

/**
Copy files, using two techniques, FileChannels and streams.
Using FileChannels is usually faster than using streams.
*/
public final class CopyFiles {

 /* Change these settings before running this class. */

 /** The file to be copied. */
 public static final String INPUT_FILE = "C:\\TEMP\\cottage.jpg";

 /**
  The name of the copy to be created by this class.
  If this file doesn't exist, it will be created, along with any
  needed parent directories.
 */
 public static final String COPY_FILE_TO = "C:\\TEMP10\\cottage_2.jpg";

 /** Run the example. */
 public static void main(String... aArgs) throws IOException{
   File source = new File(INPUT_FILE);
   File target = new File(COPY_FILE_TO);
   CopyFiles test = new CopyFiles();
   test.copyWithChannels(source, target, false);
   //test.copyWithStreams(source, target, false);
   log("Done.");
 }

 /** This may fail for VERY large files. */
 private void copyWithChannels(File aSourceFile, File aTargetFile, boolean aAppend) {
   log("Copying files with channels.");
   ensureTargetDirectoryExists(aTargetFile.getParentFile());
   FileChannel inChannel = null;
   FileChannel outChannel = null;
   FileInputStream inStream = null;
   FileOutputStream outStream = null;
   try{
     try {
       inStream = new FileInputStream(aSourceFile);
       inChannel = inStream.getChannel();
       outStream = new  FileOutputStream(aTargetFile, aAppend);
       outChannel = outStream.getChannel();
       long bytesTransferred = 0;
       //defensive loop - there's usually only a single iteration :
       while(bytesTransferred < inChannel.size()){
         bytesTransferred += inChannel.transferTo(0, inChannel.size(), outChannel);
       }
     }
     finally {
       //being defensive about closing all channels and streams
       if (inChannel != null) inChannel.close();
       if (outChannel != null) outChannel.close();
       if (inStream != null) inStream.close();
       if (outStream != null) outStream.close();
     }
   }
   catch (FileNotFoundException ex){
     log("File not found: " + ex);
   }
   catch (IOException ex){
     log(ex);
   }
 }

 private void copyWithStreams(File aSourceFile, File aTargetFile, boolean aAppend) {
   log("Copying files with streams.");
   ensureTargetDirectoryExists(aTargetFile.getParentFile());
   InputStream inStream = null;
   OutputStream outStream = null;
   try{
     try {
       byte[] bucket = new byte[32*1024];
       inStream = new BufferedInputStream(new FileInputStream(aSourceFile));
       outStream = new BufferedOutputStream(new FileOutputStream(aTargetFile, aAppend));
       int bytesRead = 0;
       while(bytesRead != -1){
         bytesRead = inStream.read(bucket); //-1, 0, or more
         if(bytesRead > 0){
           outStream.write(bucket, 0, bytesRead);
         }
       }
     }
     finally {
       if (inStream != null) inStream.close();
       if (outStream != null) outStream.close();
     }
   }
   catch (FileNotFoundException ex){
     log("File not found: " + ex);
   }
   catch (IOException ex){
     log(ex);
   }
 }

 private void ensureTargetDirectoryExists(File aTargetDir){
   if(!aTargetDir.exists()){
     aTargetDir.mkdirs();
   }
 }

 private static void log(Object aThing){
   System.out.println(String.valueOf(aThing));
 }
}