修改版的java導入編碼問題(方法)

/**
	 * 判斷文件的編碼格式
	 * 
	 * @param sourceFile
	 * @return
	 */
	private static String getFilecharset(File sourceFile) {
		String charset = "UTF-8";
		byte[] first3Bytes = new byte[3];
		try {
			boolean checked = false;
			BufferedInputStream bis = new BufferedInputStream(
					new FileInputStream(sourceFile));
			bis.mark(0);
			int read = bis.read(first3Bytes, 0, 3);
			if (read == -1) {
				return charset; // 文件編碼爲 ANSI
			} else if (first3Bytes[0] == (byte) 0xFF
					&& first3Bytes[1] == (byte) 0xFE) {
				charset = "UTF-16LE"; // 文件編碼爲 Unicode
				checked = true;
			} else if (first3Bytes[0] == (byte) 0xFE
					&& first3Bytes[1] == (byte) 0xFF) {
				charset = "UTF-16BE"; // 文件編碼爲 Unicode big endian
				checked = true;
			} else if (first3Bytes[0] == 49 && first3Bytes[1] == -60
					&& first3Bytes[2] == -29) {
				charset = "gb2312"; // 文件編碼爲 ANSI
				checked = true;
			} else if (first3Bytes[0] == 49 && first3Bytes[1] == -95
					&& first3Bytes[2] == -94) {
				charset = "gb2312"; // 文件編碼爲 ANSI
				checked = true;
			} else if (first3Bytes[0] == -51 && first3Bytes[1] == -8
					&& first3Bytes[2] == -62) {
				charset = "gb2312"; // 文件編碼爲 ANSI
				checked = true;
			}
			bis.reset();
			if (!checked) {
				int loc = 0;
				while ((read = bis.read()) != -1) {
					loc++;
					if (read >= 0xF0)
						break;
					if (0x80 <= read && read <= 0xBF) // 單獨出現BF以下的，也算是GBK
						break;
					if (0xC0 <= read && read <= 0xDF) {
						read = bis.read();
						if (0x80 <= read && read <= 0xBF) // 雙字節 (0xC0 - 0xDF)
							// (0x80
							// - 0xBF),也可能在GB編碼內
							continue;
						else
							break;
					} else if (0xE0 <= read && read <= 0xEF) {// 也有可能出錯，但是機率較小
						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;
	}