关于IO复制文件的问题 求解！

import *;
class  FileDemo
{
    public static void main(String[] args) throws IOException
    {
        if(args.length !=2)
        {
            System.out.println(
                    "Usage:  java copy souceFile targetDir（路径）");
                    System.exit(0);
        }
        //提取原文件名
        String sourceFile = args[0].trim();
        String sourceFileName = sourceFile.substring(sourceFile.lastIndexOf("\\")+1);
        //构造目标文件名
        String targetFileName = sourceFileName.substring(0,sourceFileName.lastIndexOf('.'))+".txt";
        //省略源、目标文件判断,操作文件
        FileReader fr = new FileReader(sourceFile);
        FileWriter fw = new FileWriter(args[1]+targetFileName);
        BufferedReader br = new BufferedReader(fr);
        BufferedWriter bw = new BufferedWriter(fw);
        int ch =0;
        while((ch=br.read()) != -1)
        {
            bw.write(ch);
        }
        br.close();
        bw.close();
    }
}