Use Java 11 language features where possible (#237)

Author: basil

src/main/java/winstone/HostConfiguration.java

@@ -26,12 +26,12 @@
 import java.lang.reflect.Constructor;
 import java.nio.file.Files;
 import java.nio.file.InvalidPathException;
-import java.util.Collections;
 import java.util.Enumeration;
 import java.util.Hashtable;
 import java.util.Map;
 import java.util.Map.Entry;
 import java.util.Properties;
+import java.util.Set;
 import java.util.StringTokenizer;
 import java.util.jar.JarEntry;
 import java.util.jar.JarFile;
@@ -184,7 +184,7 @@ public void postConfigure() throws Exception {
         wac.getSecurityHandler().setLoginService(loginService);
         wac.setThrowUnavailableOnStartupException(true);    // if boot fails, abort the process instead of letting empty Jetty run
         wac.setMimeTypes(mimeTypes);
-        wac.getSessionHandler().setSessionTrackingModes(Collections.singleton(SessionTrackingMode.COOKIE));
+        wac.getSessionHandler().setSessionTrackingModes(Set.of(SessionTrackingMode.COOKIE));
         wac.getSessionHandler().setSessionCookie(WinstoneSession.SESSION_COOKIE_NAME);
         this.webapps.put(wac.getContextPath(),wac);
         return wac;

src/test/java/winstone/FormSubmissionTest.java

@@ -34,11 +34,7 @@ public void largeForm() throws Exception {
         for (int size = 1; size <= 9_999_999; size *= 3) {
             System.out.println("trying size " + size);
             WebRequest wreq = new PostMethodWebRequest("http://127.0.0.2:"+port+"/AcceptFormServlet");
-            StringBuilder b = new StringBuilder();
-            for (int i = 0; i < size; i++) {
-                b.append('.');
-            }
-            wreq.setParameter("x", b.toString());
+            wreq.setParameter("x", ".".repeat(size));
             WebResponse wresp = wc.getResponse(wreq);
             try (InputStream content = wresp.getInputStream()) {
                 assertTrue("Loading AcceptFormServlet at size " + size, content.available() > 0);