第四次作业

import java.io.FileInputStream;

import java.io.FileOutputStream;

import java.io.IOException;

public class CopyFile {

       /**

        * @param args

        */

       public static void main(String[] args) {

              try {

                     FileInputStream fis = new FileInputStream ("a.jpg");

                     FileOutputStream fos = new FileOutputStream ("temp.jpg");

                     int read = fis.read();            

                     while ( read != -1 ) {

                            fos.write(read);     

                            read = fis.read();

                     }                  

                     fis.close();

                     fos.close();

              } catch (IOException e) {

                     e.printStackTrace();

              }

       }

}

但是，这段代码在复制如mp3等大文件时，运行效率很低，即运行时间长。

下面是改进的代码

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.channels.FileChannel;


public class fileChannelCopy {

    /**
     * @param args
     */
    public static void fileChannelCopy(File a ,File b){
        FileInputStream fi = null;
        FileOutputStream fo = null;
        FileChannel in = null;
        FileChannel out = null;
        
        try {
            fi = new FileInputStream(a);
            fo = new FileOutputStream(b);
            in = fi.getChannel();
            out = fo.getChannel();
            try {
                in.transferTo(0, in.size(), out);
                 fi.close();

                    in.close();

                    fo.close();

                    out.close();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } 
    }
      
    public static void main(String[] args) {
        // TODO Auto-generated method stub
     File a = new File("a.mp3");
     File b = new File("temp.jpg");
     fileChannelCopy(a,b);
    }

}