Android中Java根据文件头获取文件类型的方法

public class FileType {
  public static final HashMap mFileTypes = new HashMap();
  static {
    //images
    mFileTypes.put("FFD8FF", "jpg");
    mFileTypes.put("89504E47", "png");
    mFileTypes.put("47494638", "gif");
    mFileTypes.put("49492A00", "tif");
    mFileTypes.put("424D", "bmp");
    //
    mFileTypes.put("41433130", "dwg"); //CAD
    mFileTypes.put("38425053", "psd");
    mFileTypes.put("7B5C727466", "rtf"); //日记本
    mFileTypes.put("3C3F786D6C", "xml");
    mFileTypes.put("68746D6C3E", "html");
    mFileTypes.put("44656C69766572792D646174653A", "eml"); //邮件
    mFileTypes.put("D0CF11E0", "doc");
    mFileTypes.put("5374616E64617264204A", "mdb");
    mFileTypes.put("252150532D41646F6265", "ps");
    mFileTypes.put("255044462D312E", "pdf");
    mFileTypes.put("504B0304", "zip");
    mFileTypes.put("52617221", "rar");
    mFileTypes.put("57415645", "wav");
    mFileTypes.put("41564920", "avi");
    mFileTypes.put("2E524D46", "rm");
    mFileTypes.put("000001BA", "mpg");
    mFileTypes.put("000001B3", "mpg");
    mFileTypes.put("6D6F6F76", "mov");
    mFileTypes.put("3026B2758E66CF11", "asf");
    mFileTypes.put("4D546864", "mid");
    mFileTypes.put("1F8B08", "gz");
    mFileTypes.put("", "");
    mFileTypes.put("", "");
  }
  public static String getFileType(String filePath) {
    return mFileTypes.get(getFileHeader(filePath));
  }
  //获取文件头信息
  public static String getFileHeader(String filePath) {
    FileInputStream is = null;
    String value = null;
    try {
      is = new FileInputStream(filePath);
      byte[] b = new byte[3];
      is.read(b, 0, b.length);
      value = bytesToHexString(b);
    } catch (Exception e) {
    } finally {
      if(null != is) {
        try {
          is.close();
        } catch (IOException e) {}
      }
    }
    return value;
  }
  private static String bytesToHexString(byte[] src){
     StringBuilder builder = new StringBuilder();
     if (src == null || src.length <= 0) {
       return null;
     }
     String hv;
     for (int i = 0; i