/** The key of the message: 7z Archive */
    public static final String LABELS_facet_filetype_7z = "{labels.facet_filetype_7z}";

    /** The key of the message: Bz Archive */
    public static final String LABELS_facet_filetype_bz = "{labels.facet_filetype_bz}";

    /** The key of the message: Bz2 Archive */

hex_digits     = hex_digit { [ "_" ] hex_digit } .
</pre>

<pre>
42
4_2
0600
0_600
0o600
0O600       // second character is capital letter 'O'
0xBadFace
0xBad_Face
0x_67_7a_2f_cc_40_c6
170141183460469231731687303715884105727
170_141183_460469_231731_687303_715884_105727

_42         // an identifier, not an integer literal