获得文本文件编码格式

   private String initBookEncode(FileInputStream fileInputStream) {
        String encode = "gb2312";
    	try{
            byte[] head = new byte[3];  
            fileInputStream.read(head);
            if(head[0]==-17 && head[1]==-69 && head[2] ==-65)  
            	encode = "UTF-8";
            else if (head[0] == -1 && head[1] == -2 )  
            	encode = "UTF-16";  
            else if (head[0] == -2 && head[1] == -1 )  
            	encode = "Unicode"; 
    	}catch (IOException e) {
            Log.e(Global.TAG, "can't get book encoding:"+e.getMessage());
		}
    	return encode;
    }