def _escape_char(in_c):
    """
    Escape some special characters in java .properties files.

    :param in_c: Input character

    >>> "\\:" == _escape_char(':')
    True
    >>> "\\=" == _escape_char('=')
    True
    >>> _escape_char('a')
    'a'
    """
    return '\\' + in_c if in_c in ('"', '\'', '\\') else in_c