### Question:
MediaWikiUtil { static String removeBetween(String string, char begin1, char begin2, char end1, char end2) { if (string.length() < 2) { return string; } CharStack charStack = new CharStack(); charStack.push(string.charAt(0)); for (int idx = 1; idx < string.length(); idx++) { char previous = string.charAt(idx - 1); char current = string.charAt(idx); if (current == end2 && previous == end1) { while (charStack.length() > 1) { if (charStack.pop() == begin2 && charStack.peek() == begin1) { charStack.pop(); if (idx < string.length() - 1 && string.charAt(idx + 1) == end1) { idx++; } break; } } charStack.push(' '); } else { charStack.push(current); } } return charStack.toString(); } private  MediaWikiUtil(); static String stripMediaWikiMarkup(String markup); static String extractSentences(String text); static final WikiPage retrieveArticle(MediaWikiDescriptor descriptor, String title); static final List<WikiPageReference> retrieveArticlesForCategory(MediaWikiDescriptor descriptor,
            String categoryName); static final WikiPageReference retrieveRandomArticle(MediaWikiDescriptor descriptor); static final List<WikiPageReference> retrieveBacklinks(MediaWikiDescriptor descriptor, String pageName); static WikiTemplate extractTemplate(String markup); static List<String> getNamedMarkup(String markup, String... names); static void parseDump(File wikipediaDump, Consumer<WikiPage> action, ProgressReporter progress); static void parseDump(File wikipediaDump, Consumer<WikiPage> action); static void parseDump(InputStream inputStream, Consumer<WikiPage> action); static void main(String[] args); static final Pattern HEADING_PATTERN; static final Pattern INTERNAL_LINK_PATTERN; static final Pattern REDIRECT_PATTERN; }### Answer:
@Test public void testRemoveBetween() { assertEquals(" c f", MediaWikiUtil.removeBetween("{{{{a}}b}}c{{d{{e}}}}f", '{', '{', '}', '}')); assertEquals(" c", MediaWikiUtil.removeBetween("{{{{a}}b}}c", '{', '{', '}', '}')); assertEquals("a \n\nb", MediaWikiUtil.removeBetween("a{{c}}\n\nb", '{', '{', '}', '}')); assertEquals("abc gh l", MediaWikiUtil.removeBetween("abc {{d:{{e{{f}}}}}} gh {{ijk}} l", '{', '{', '}', '}')); }