filecopy.java

有关java的源程序,为讲授java程序设计课程使用

import java.io.*;
class FileCopy
{
	public static void main(String []args)
	{
		if(args.length !=2)
			 System.out.println("Usage:java FileCopy"+ "<Source File> <Dest File>");
		else
		{
			try{
				copy(args[0],args[1]);
			}
			catch(IOException e)
			{
				System.out.println(e.getMessage());
			}
		}
	}
	public static void copy(String srcfile, String dstfile) throws IOException
	{
		byte [] buf;
		int bytes;
		File src=new File(srcfile);
		File dst=new File(dstfile);
		FileInputStream srcs=null;
		FileOutputStream dsts=null;
		try
		{
			if(! src.exists() || ! src.isFile())
				throw new FileCopyException("FileCopy"+"no such source File:"+srcfile);
			if(!src.canRead())
				throw new FileCopyException("FileCopy:"+"source file is unreadable:"+srcfile);
			if(dst.exists())
			{
				if(dst.isFile())
				{
					if(! dst.canWrite())
						throw new FileCopyException("FileCopy:"+"dest file is unWriteable:"+dstfile);
					System.out.print("File"+dstfile+"already exists, OverWrite ?(Y/N):");
					System.out.flush();
					String resp=new DataInputStream(System.in).readLine();
					if(!resp.equals("Y")&& !resp.equals("y"))
						throw new FileCopyException("FileCopy:"+"copy cancelled.");
				}
				else
				{
					throw new FileCopyException("FileCopy:"+"dest is not a file:"+dstfile);
				}
			}
			else
			{
				File parent=parent(dst);
				if(!parent.exists())
					throw new FileCopyException("FileCopy:"+"dest directory doesn't exists:"+dstfile);
				if(!parent.canWrite())
					throw new FileCopyException("FileCopy:"+"dest directory is unwriteable:"+dstfile);
			}
			srcs=new FileInputStream(src);
			dsts=new FileOutputStream(dst);
			buf=new byte[1024];
			while((bytes=srcs.read(buf))!=-1)
				dsts.write(buf,0,bytes);
		}
		finally
		{
			if(srcs !=null)
				try
				{
					srcs.close();
				}
				catch(IOException e)
				{
				}
			if(dsts !=null)
				try 
				{
					dsts.close();
				}
				catch(IOException e)
				{
				}
		}
	}
	private static File parent(File f)
	{
		String dirname=f.getParent();
		if(dirname==null)
		{
			if(f.isAbsolute())
				return new File(File.separator);
			else
				return new File(System.getProperty("user.dir"));
		}
		return new File(dirname);
	}
}
class FileCopyException extends IOException
{
	public FileCopyException(String msg)
	{
		super(msg);
	}
}