为什么如下方法把inputstream转为String的时候会出错？

public String getWeatherJson(InputStream is) {

		StringBuilder builder = new StringBuilder();

		InputStream is = null;	

		try {				

			byte[] b = new byte[2048];

			for (int n; (n = is.read(b)) != -1;) {

				builder.append(new String(b, 0, n, "UTF-8"));

			}

		} catch (UnsupportedEncodingException e) {

			e.printStackTrace();

		} catch (IOException e) {

			e.printStackTrace();

		} finally {

			try {

				is.close();

			} catch (IOException e) {

				e.printStackTrace();

			}

		}

		return builder.toString();

	}

is本来应该的输出为：

{"weatherinfo":{"city":"门头沟","city_en":"mentougou","date_y":"2013年9月3日","date":"","week":"星期二","fchh":"11","cityid":"101011400","temp1":"27C~18C","temp2":"22C~17C","temp3":"23C~17C","temp4":"29C~16C","temp5":"29C~17C","temp6":"28C~17C","tempF1":"80.6F~64.4F","tempF2":"71.6F~62.6F","tempF3":"73.4F~62.6F","tempF4":"84.2F~60.8F","tempF5":"84.2F~62.6F","tempF6":"82.4F~62.6F","weather1":"阵雨","weather2":"中雨转小雨","weather3":"小雨转多云","weather4":"晴","weather5":"晴","weather6":"晴转多云","img1":"3","img2":"99","img3":"8","img4":"7","img5":"7","img6":"1","img7":"0","img8":"99","img9":"0","img10":"99","img11":"0","img12":"1","img_single":"3","img_title1":"阵雨","img_title2":"阵雨","img_title3":"中雨","img_title4":"小雨","img_title5":"小雨","img_title6":"多云","img_title7":"晴","img_title8":"晴","img_title9":"晴","img_title10":"晴","img_title11":"晴","img_title12":"多云","img_title_single":"阵雨","wind1":"微风","wind2":"微风","wind3":"微风","wind4":"微风","wind5":"微风","wind6":"微风","fx1":"微风","fx2":"微风","fl1":"小于3级","fl2":"小于3级","fl3":"小于3级","fl4":"小于3级","fl5":"小于3级","fl6":"小于3级","index":"热","index_d":"天气热，建议着短裙、短裤、短薄外套、T恤等夏季服装。","index48":"较舒适","index48_d":"建议着薄外套、开衫牛仔衫裤等服装。年老体弱者应适当添加衣物，宜着夹克衫、薄毛衣等。","index_uv":"弱","index48_uv":"最弱","index_xc":"不宜","index_tr":"适宜","index_co":"较舒适","st1":"25","st2":"16","st3":"18","st4":"15","st5":"21","st6":"17","index_cl":"较不宜","index_ls":"不太适宜","index_ag":"易发"}}
但是实际上的输出是存在乱码，但是只是一两个字符乱码。
这个例子中乱码的部分是
,"wind1":"微风",中的“微”字无法正常显示。

但是通过上述方法如果复制文件的话正常。。
后来改成了如下方法：

public static String fromIputStreamToString(InputStream is){

		ByteArrayOutputStream baos = new ByteArrayOutputStream();

		int i = -1;

		try {

			while ((i = is.read()) != -1) {

				baos.write(i);

			}

		} catch (IOException e) {

			// TODO Auto-generated catch block

			e.printStackTrace();

		}

		return baos.toString();