自动识别txt编码读取文本，防止乱码

	
	/**
	 * 得到文件字符集名称
	 *
	 * @param file 文件
	 *
	 * @return {@link String}
	 *
	 * @throws Exception 异常
	 */
	private static String getFileCharsetName(String filePath) throws Exception {
		String charset = "GBK";
		byte[] first3Bytes = new byte[3];
		try {
			boolean checked = false;
			BufferedInputStream bis = new BufferedInputStream(new FileInputStream(filePath));
			bis.mark(0);
			int read = bis.read(first3Bytes, 0, 3);
			if (read == - 1) {
				//文件编码为 ANSI
				return charset;
			} else if (first3Bytes[0] == (byte) 0xFF
					&& first3Bytes[1] == (byte) 0xFE) {
				//文件编码为 Unicode
				charset = "UTF-16LE";
				checked = true;
			} else if (first3Bytes[0] == (byte) 0xFE
					&& first3Bytes[1] == (byte) 0xFF) {
				//文件编码为 Unicode big endian
				charset = "UTF-16BE";
				checked = true;
			} else if (first3Bytes[0] == (byte) 0xEF
					&& first3Bytes[1] == (byte) 0xBB
					&& first3Bytes[2] == (byte) 0xBF) {
				//文件编码为 UTF-8
				charset = "UTF-8";
				checked = true;
			}
			bis.reset();
			if (! checked) {
				int loc = 0;
				while ((read = bis.read()) != - 1) {
					loc++;
					if (read >= 0xF0) {
						break;
					}
					if (0x80 <= read && read <= 0xBF) {
						// 单独出现BF如下的，也算是GBK
						break;
					}
					if (0xC0 <= read && read <= 0xDF) {
						read = bis.read();
						if (0x80 <= read && read <= 0xBF) {
							// 双字节 (0xC0 - 0xDF)
							// (0x80
							// - 0xBF),也可能在GB编码内
							continue;
						} else {
							break;
						}
					} else if (0xE0 <= read && read <= 0xEF) {
						// 也有可能出错，可是概率较小
						read = bis.read();
						if (0x80 <= read && read <= 0xBF) {
							read = bis.read();
							if (0x80 <= read && read <= 0xBF) {
								charset = "UTF-8";
								break;
							} else {
								break;
							}
						} else {
							break;
						}
					}
				}
			}
			bis.close();
		} catch (Exception e) {
			e.printStackTrace();
		}
		return charset;
	}