diff -r e947a3a50a95 -r 634d8e14c172 src/jdk.incubator.httpclient/share/classes/jdk/incubator/http/ImmutableHeaders.java
--- a/src/jdk.incubator.httpclient/share/classes/jdk/incubator/http/ImmutableHeaders.java	Sun Nov 05 17:05:57 2017 +0000
+++ b/src/jdk.incubator.httpclient/share/classes/jdk/incubator/http/ImmutableHeaders.java	Sun Nov 05 17:32:13 2017 +0000
@@ -38,7 +38,7 @@
 import static java.util.Collections.unmodifiableMap;
 import static java.util.Objects.requireNonNull;
 
-final class ImmutableHeaders implements HttpHeaders {
+final class ImmutableHeaders extends HttpHeaders {
 
     private final Map<String, List<String>> map;
 
@@ -72,25 +72,6 @@
     }
 
     @Override
-    public Optional<String> firstValue(String name) {
-        return allValues(name).stream().findFirst();
-    }
-
-    @Override
-    public OptionalLong firstValueAsLong(String name) {
-        return allValues(name).stream().mapToLong(Long::valueOf).findFirst();
-    }
-
-    @Override
-    public List<String> allValues(String name) {
-        requireNonNull(name);
-        List<String> values = map.get(name);
-        // Making unmodifiable list out of empty in order to make a list which
-        // throws UOE unconditionally
-        return values != null ? values : unmodifiableList(emptyList());
-    }
-
-    @Override
     public Map<String, List<String>> map() {
         return map;
     }