Program: 91653
Project: 91653
Buggy source:
/** 
 * Infers a valid Unicode identifier from the given citation, or returns   {@code null} if none.This method is useful for extracting a short designation of an authority (e.g.  {@code "EPSG"}) for processing purpose. This method performs the following actions: <ul class="verbose"> <li>First, performs the same work than   {@link #getIdentifier(Citation)} except that {@code '_'}is used instead of   {@link org.apache.sis.util.iso.DefaultNameSpace#DEFAULT_SEPARATOR ':'}as the separator between the codespace and the code.</li> <li>If the result of above method call is   {@code null} or is not a{@linkplain org.apache.sis.util.CharSequences#isUnicodeIdentifier valid Unicode identifier}, then return   {@code null}.</li> <li>Otherwise remove the   {@linkplain Character#isIdentifierIgnorable(int) ignorable characters}, if any, and returns the result.</li> </ul> <div class="note"><b>Note:</b> examples of ignorable identifier characters are <cite>zero width space</cite> or <cite>word joiner</cite>. Those characters are illegal in XML identifiers, and should therfore be removed if the Unicode identifier may also be used as XML identifier.</div> If non-null, the result is suitable for use as a XML identifier except for a few uncommon characters. <div class="note"><b>Note:</b> the following characters are invalid in XML identifiers. However since they are valid in Unicode identifiers, they could be included in the string returned by this method: <ul> <li>  {@code µ}</li> <li>  {@code ª} (feminine ordinal indicator)</li><li> {@code º} (masculine ordinal indicator)</li><li> {@code ⁔}</li> </ul></div>
 * @param citation  the citation for which to get the Unicode identifier, or {@code null}.
 * @return a non-empty Unicode identifier for the given citation without leading or trailing whitespaces,or  {@code null} if the given citation is null or does not have any Unicode identifier or title.
 * @see org.apache.sis.metadata.iso.ImmutableIdentifier
 * @see org.apache.sis.referencing.IdentifiedObjects#getUnicodeIdentifier(IdentifiedObject)
 * @see org.apache.sis.util.CharSequences#isUnicodeIdentifier(CharSequence)
 * @since 0.6
 */
public static String getUnicodeIdentifier(final Citation citation){
  return org.apache.sis.internal.util.Citations.removeIgnorableCharacters(org.apache.sis.internal.util.Citations.getIdentifier(citation,true));
}

Fixed version (ground truth):
/** 
 * Infers a valid Unicode identifier from the given citation, or returns   {@code null} if none.This method is useful for extracting a short designation of an authority (e.g.  {@code "EPSG"}) for processing purpose. This method performs the following actions: <ul class="verbose"> <li>First, performs the same work than   {@link #getIdentifier(Citation)} except that {@code '_'}is used instead of   {@link org.apache.sis.util.iso.DefaultNameSpace#DEFAULT_SEPARATOR ':'}as the separator between the codespace and the code.</li> <li>If the result of above method call is   {@code null} or is not a{@linkplain org.apache.sis.util.CharSequences#isUnicodeIdentifier valid Unicode identifier}, then return   {@code null}.</li> <li>Otherwise remove the   {@linkplain Character#isIdentifierIgnorable(int) ignorable characters}, if any, and returns the result.</li> </ul> <div class="note"><b>Note:</b> examples of ignorable identifier characters are <cite>zero width space</cite> or <cite>word joiner</cite>. Those characters are illegal in XML identifiers, and should therfore be removed if the Unicode identifier may also be used as XML identifier.</div> If non-null, the result is suitable for use as a XML identifier except for a few uncommon characters. <div class="note"><b>Note:</b> the following characters are invalid in XML identifiers. However since they are valid in Unicode identifiers, they could be included in the string returned by this method: <ul> <li>  {@code µ}</li> <li>  {@code ª} (feminine ordinal indicator)</li><li> {@code º} (masculine ordinal indicator)</li><li> {@code ⁔}</li> </ul></div>
 * @param citation  the citation for which to get the Unicode identifier, or {@code null}.
 * @return a non-empty Unicode identifier for the given citation without leading or trailing whitespaces,or  {@code null} if the given citation is null or does not have any Unicode identifier or title.
 * @see org.apache.sis.metadata.iso.ImmutableIdentifier
 * @see org.apache.sis.referencing.IdentifiedObjects#getSimpleNameOrIdentifier(IdentifiedObject)
 * @see org.apache.sis.util.CharSequences#isUnicodeIdentifier(CharSequence)
 * @since 0.6
 */
public static String getUnicodeIdentifier(final Citation citation){
  return org.apache.sis.internal.util.Citations.removeIgnorableCharacters(org.apache.sis.internal.util.Citations.getIdentifier(citation,true));
}