### Question:
AbstractLinkProvider implements Serializable { protected static String escapeForUrl(final String string) { if (string == null) { return null; } try { return URLEncoder.encode(string.replace(' ', '_'), "UTF8"); } catch (UnsupportedEncodingException e) { return null; } }  static AbstractLinkProvider fromParams(final AbstractAllParams<?> all); void addLinkToNode(final Node node, final String title); abstract String provideLink(final String title);  }### Answer:
@Test public void testEscapeForUrl() { assertEquals("abc%3A%C3%84%C3%B6%C3%BC_%C3%9F%E3%83%A1%E3%82%A4%E3%83%B3%E3%83%9A%E3%83%BC%E3%82%B8", AbstractLinkProvider.escapeForUrl("abc:Äöü ßメインページ")); }
@Test public void testEscapeForUrlNull() { assertEquals(null, AbstractLinkProvider.escapeForUrl(null)); }