BufferedReader与BufferedInputStream重复缓冲?

[jdgdf566]

FileInputStream fis = new FileInputStream(file);
BufferedReader = new BufferedReader(new InputStreamReader(new BufferedInputStream(fis),  
         "utf-8"));

第二句有两个Buffered类，会不会造成重复缓冲?

下面的代码，自动判断文本流的字符集，完全准确吗？有没有例外的、判断不正确的情况？

            FileInputStream fis = new FileInputStream(file);
            BufferedReader reader;
            BufferedInputStream in = new BufferedInputStream(fis);

            in.mark(4);
            byte[] first3bytes = new byte[3];
            in.read(first3bytes);
            in.reset();
            if (first3bytes[0] == (byte) 0xEF
                && first3bytes[1] == (byte) 0xBB
                && first3bytes[2] == (byte) 0xBF) {// utf-8
 
                reader = new BufferedReader(new InputStreamReader(in,
                     "utf-8"));
 
            } else if (first3bytes[0] == (byte) 0xFF
                && first3bytes[1] == (byte) 0xFE) {
 
                reader = new BufferedReader(new InputStreamReader(in,
                     "unicode"));
            } else if (first3bytes[0] == (byte) 0xFE
                && first3bytes[1] == (byte) 0xFF) {
 
                reader = new BufferedReader(new InputStreamReader(in,
                     "utf-16be"));
            } else if (first3bytes[0] == (byte) 0xFF
                && first3bytes[1] == (byte) 0xFF) {
 
               reader = new BufferedReader(new InputStreamReader(in,
                     "utf-16le"));
            } else {
 
               reader = new BufferedReader(new InputStreamReader(in,
                     "GBK"));
            }

[oh_Maxy]

其实LZ完全可以自己做个小例子试试嘛~