java纯文本文件拷贝

/**
	 * 拷贝大于指定行号的数据
	 * @param resource
	 * @param target
	 * @return
	 */
	public static String TxtToTxt(String resource,String resCode,String target,String tarCode,int num){
		String code1 , code2;
		if(resCode!=null &&!"".equals(resCode)){
				code1 = resCode;
		}else{
			code1 = "iso8859-1";
		}
		if(tarCode!=null &&!"".equals(tarCode)){
			code2 = resCode;
		}else{
			code2 = "iso8859-1";
		}
		FileInputStream in1 = null;
		FileOutputStream out1 = null;
		 try {
		      File file_in = new java.io.File(resource);
		      File file_out = new java.io.File(target);
		       in1 = new FileInputStream(file_in);
		      InputStreamReader isr = new InputStreamReader(in1,code1);
		      BufferedReader br = new BufferedReader(isr);
		      
		       out1 = new FileOutputStream(file_out);
		      OutputStreamWriter osw = new OutputStreamWriter(out1,code2);
		      BufferedWriter bw = new BufferedWriter(osw);
		      int i=0;
		      String s = "";
		      while(br.ready()){
		    	i++;
		    	s = br.readLine()+"\n";
		    	if(i>num){
		    	bw.write(s, 0, s.length());
		    	}
		      }
		      bw.flush(); //刷新缓冲区,如果不加的话,会奇怪的少几行
		      
		    }catch (Exception e) {
		          e.printStackTrace();
		    }finally{
		    	try {
					in1.close();
					out1.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
		    }

		return "";
	}