Fix LinkTest failure due to leading whitespace and simplify code

Fixes eclipse-platform#561

ua/org.eclipse.ua.tests.doc/src/org/eclipse/ua/tests/doc/internal/linkchecker/LinkTest.java

@@ -28,6 +28,8 @@
 import java.util.Objects;
 import java.util.Set;
 import java.util.TreeSet;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
 
 import org.eclipse.core.runtime.NullProgressMonitor;
 import org.eclipse.core.runtime.Platform;
@@ -101,17 +103,14 @@ public void addHits(List<SearchHit> hits, String wordsSearched) {
  assertEquals(Collections.emptySet().toString(), linkFailures.toString());
  }
 
+ private static final Pattern HREF = Pattern.compile("<a href=\"([^\"]+)\"");
+
  private Set<String> checkLinks(InputStream stream, URI currentDoc, Set<URI> knownPagesURIs) throws IOException {
  Set<String> res = new HashSet<>();
  try (BufferedReader in = new BufferedReader(new InputStreamReader(stream))) {
- String inputLine;
- while ((inputLine = in.readLine()) != null) {
- int index = 0;
- while ((index = inputLine.indexOf("<a href=\"", index)) > 0) {
- int closeIndex = inputLine.indexOf('"', index + "<a href=\"".length());
- URI href = URI
- .create(inputLine.substring(index + "<a href=\"".length(), closeIndex).replace(" ", "%20"));
- index = closeIndex;
+ for (String inputLine; (inputLine = in.readLine()) != null;) {
+ for (Matcher matcher = HREF.matcher(inputLine); matcher.find();) {
+ URI href = URI.create(matcher.group(1).replace(" ", "%20"));
  if (href.isAbsolute()) {
  continue;
  }