### Question:
CSSURLHelper { @Nullable public static String getURLValue (@Nullable final String sValue) { if (isURLValue (sValue)) { return CSSParseHelper.trimUrl (sValue); } return null; } private  CSSURLHelper(); static boolean isURLValue(@Nullable final String sValue); @Nullable static String getURLValue(@Nullable final String sValue); @Nonnull @Nonempty static String getAsCSSURL(@Nonnull final ISimpleURL aURL, final boolean bQuoteURL); static boolean isValidCSSURLChar(final char c); static boolean isCSSURLRequiringQuotes(@Nonnull final String sURL); @Nonnull @Nonempty static String getEscapedCSSURL(@Nonnull final String sURL, final char cQuoteChar); @Nonnull @Nonempty static String getAsCSSURL(@Nonnull final String sURL, final boolean bForceQuoteURL); static final boolean DEFAULT_QUOTE_URLS; }### Answer:
@Test public void testGetURLValue () { assertEquals ("a.gif", CSSURLHelper.getURLValue ("url(a.gif)")); assertEquals ("a.gif", CSSURLHelper.getURLValue ("url('a.gif')")); assertEquals ("a.gif", CSSURLHelper.getURLValue ("url(\"a.gif\")")); assertEquals ("a.gif?x=y", CSSURLHelper.getURLValue ("url(\"a.gif?x=y\")")); assertEquals ("a.gif", CSSURLHelper.getURLValue ("url(\"\\a.gif\")")); assertEquals ("\"a.gif?x=y'", CSSURLHelper.getURLValue ("url(\"a.gif?x=y')")); assertNull (CSSURLHelper.getURLValue ("url(a.gif")); assertNull (CSSURLHelper.getURLValue ("url (a.gif)")); }