Write a program to copy all the .java files in the d:\java directory to the d:\jad directory and change the extension of the original files from .java to .jad

1. Write a program to copy all the .java files in the d:\java directory to the d:\jad directory, and change the extension of the original file from .java to .jad

 

package copy;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.FilenameFilter;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

public class CopyTest {
           public static void main(String[] args) throws Exception {
            File file = new File( " D:\\java " );
             // Determine whether the directory exists 
            if (!(file.exists()&& file.isDirectory())){
                 throw  new Exception( "The directory does not exist " );
            }
            // find the .java file under the folder 
            File[] files=file.listFiles( new FilenameFilter() {
                 public boolean accept(File dir, String name) {
                     // TODO Auto-generated method stub 
                    return name.endsWith( " . java " );
                }
            });
            System.out .println ( files.length );
             // Copy the file
             // Find the target directory 
            File targetfile= new File( " D:\\jad " );
             // Determine whether the directory exists, create 
            if (!(targetfile) .exists()&& targetfile.isDirectory())){
                targetfile.mkdirs();
            }
            // Replace file name 
            for (File f:files){
 //                 1. Use file stream to achieve file copy 
                String targetFilename=f.getName().replace( " .java " , " .jad " );
 //                 FileInputStream in= new FileInputStream(f);
 //                 FileOutputStream out=new FileOutputStream(new File(targetfile,targetFilename));
 //                 copy(in,out);
 //                 2. Use buffered streams to speed up reading and writing 
                BufferedInputStream bis= new BufferedInputStream( new FileInputStream(f));
                BufferedOutputStream bos=new BufferedOutputStream(new FileOutputStream(new File(targetfile,targetFilename)));
                CopyDemo2(bis,bos);
            }
            
        }
           
           /**
            * Use file stream to achieve file copy
            * @author smy
            * @throws Exception
            */
        public static void copy(InputStream in,OutputStream out) throws Exception{
            byte[] data = new byte[1024*10];
            int len = -1;
            while((len = in.read(data))!=-1){
                out.write(data,0,len);
            }    
            
            in.close();
            out.close();
        }
           
        /**
         * Use buffered streams to speed up read and write efficiency
         *
         * Buffered streams are a pair of high-level streams that use them to improve reading
         * Write efficiency.
         *
         * Advanced Streams: Advanced Streams are used to process other streams, Advanced Streams cannot
         * exists independently, because there is no sense, the purpose of using advanced streams
         * is to address the complexity of some read and write operations. simplify us
         * read and write operations.
         *
         * Low-level stream: The data source is clear, and the stream that is really responsible for reading and writing data.
         *
         * Read and write operations must require low-level streams, but they do not have to be used
         * Advanced Streaming.
         * @author SMY
         * @throws Exception
         */
        public static void CopyDemo2(InputStream bis,OutputStream bos) throws Exception{
            int d = -1;
            /*
             * The buffer stream internally maintains a byte array as
             * Buffer. When we call the read() method to read a
             * bytes, the buffered stream will read several bytes at a time
             * and store in the buffer, then return the first byte, when
             * When we call the read method again to read a byte,
             * it will immediately return the second byte in the buffer,
             * will not happen again until all bytes have been returned
             * The actual read operation, reads a set of bytes into the buffer
             * Area.
             * So in essence, by reading several bytes at a time,
             * Reduce the number of reads and improve the read efficiency.
             */
            while((d=bis.read())!=-1){
                bos.write(d);
            }
            bis.close();
            bos.close();    
        }
        
}