### Question:
HttpResponseBuilder extends MutableContent { public HttpResponseBuilder setCacheTtl(int cacheTtl) { headers.removeAll("Pragma"); headers.removeAll("Expires"); headers.replaceValues("Cache-Control", ImmutableList.of("public,max-age=" + cacheTtl)); incrementNumChanges(); return this; } HttpResponseBuilder(GadgetHtmlParser parser, HttpResponse response);  HttpResponseBuilder();  HttpResponseBuilder(HttpResponseBuilder builder);  HttpResponseBuilder(HttpResponse response); HttpResponse create(); HttpResponseBuilder setResponseString(String body); HttpResponseBuilder setEncoding(Charset charset); HttpResponseBuilder setResponse(byte[] responseBytes); HttpResponseBuilder setResponseNoCopy(byte[] responseBytes); HttpResponseBuilder setHttpStatusCode(int httpStatusCode); HttpResponseBuilder clearAllHeaders(); HttpResponseBuilder addHeader(String name, String value); HttpResponseBuilder setHeader(String name, String value); String getHeader(String name); HttpResponseBuilder addHeaders(Map<String, String> headers); HttpResponseBuilder addAllHeaders(Map<String, ? extends List<String>> headers); Collection<String> removeHeader(String name); HttpResponseBuilder setCacheTtl(int cacheTtl); HttpResponseBuilder setExpirationTime(long expirationTime); HttpResponseBuilder setStrictNoCache(); HttpResponseBuilder setMetadata(String key, String value); HttpResponseBuilder setMetadata(Map<String, String> metadata); int getContentLength(); int getHttpStatusCode();  }### Answer:
@Test public void setCacheTtl() { HttpResponseBuilder builder = new HttpResponseBuilder() .addHeader("Pragma", "no-cache") .addHeader("Expires", "some time stamp normally goes here") .addHeader("Cache-Control", "no-cache") .setCacheTtl(100); Multimap<String, String> headers = builder.getHeaders(); assertFalse("Expires header not removed.", headers.containsKey("Expires")); assertFalse("Pragma header not removed", headers.containsKey("Pragma")); assertEquals("public,max-age=100", headers.get("Cache-Control").iterator().next()); }