--- /dev/null	2016-04-22 22:42:07.067228853 +0100
+++ new/src/java.httpclient/share/classes/java/net/http/WebSocketBuilderImpl.java	2016-04-25 23:11:11.749374081 +0100
@@ -0,0 +1,171 @@
+/*
+ * Copyright (c) 2015, 2016, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+package java.net.http;
+
+import java.net.URI;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.LinkedHashMap;
+import java.util.LinkedHashSet;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Locale;
+import java.util.Map;
+import java.util.Set;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.TimeUnit;
+
+import static java.lang.String.format;
+import static java.util.Objects.requireNonNull;
+
+final class WebSocketBuilderImpl implements WebSocket.Builder {
+
+    private static final Set<String> FORBIDDEN_HEADERS_LOWER_CASED = Set.of(
+            "connection", "upgrade", "sec-websocket-accept", "sec-websocket-extensions",
+            "sec-websocket-key", "sec-websocket-protocol", "sec-websocket-version");
+
+    private final URI uri;
+    private final HttpClient client;
+    private final LinkedHashMap<String, List<String>> headers = new LinkedHashMap<>();
+    private final WebSocket.Listener listener;
+    private Collection<String> subprotocols = Collections.emptyList();
+    private long timeout;
+    private TimeUnit timeUnit;
+
+    WebSocketBuilderImpl(URI uri, HttpClient client, WebSocket.Listener listener) {
+        requireNonNull(uri, "uri");
+        requireNonNull(client, "client");
+        requireNonNull(listener, "listener");
+        checkUri(uri);
+        this.uri = uri;
+        this.listener = listener;
+        this.client = client;
+    }
+
+    @Override
+    public WebSocket.Builder header(String name, String value) {
+        requireNonNull(name, "name");
+        requireNonNull(value, "value");
+        // TODO: I don't like the fact the knowledge about
+        // case-insensitivity, order and name->list(value) structure, etc.
+        // sits is in the builder
+        if (FORBIDDEN_HEADERS_LOWER_CASED.contains(name.toLowerCase(Locale.ROOT))) {
+            throw new IllegalArgumentException(
+                    format("Header '%s' is used in the WebSocket Protocol", name));
+        }
+        List<String> values = headers.computeIfAbsent(name, n -> new LinkedList<>());
+        values.add(value);
+        return this;
+    }
+
+    @Override
+    public WebSocket.Builder subprotocols(String mostPreferred, String... lesserPreferred) {
+        requireNonNull(mostPreferred, "mostPreferred");
+        requireNonNull(lesserPreferred, "lesserPreferred");
+        this.subprotocols = checkAndReturnSubprotocols(mostPreferred, lesserPreferred);
+        return this;
+    }
+
+    @Override
+    public WebSocket.Builder connectTimeout(long timeout, TimeUnit unit) {
+        if (timeout < 0) {
+            throw new IllegalArgumentException("Negative timeout: " + timeout);
+        }
+        requireNonNull(unit, "unit");
+        this.timeout = timeout;
+        this.timeUnit = unit;
+        return this;
+    }
+
+    @Override
+    public CompletableFuture<WebSocket> buildAsync() {
+        return WebSocketImpl.newInstanceAsync(this);
+    }
+
+    private static void checkUri(URI uri) {
+        String s = uri.getScheme();
+        if (!("ws".equalsIgnoreCase(s) || "wss".equalsIgnoreCase(s))) {
+            throw new IllegalArgumentException
+                    ("URI scheme not ws or wss (RFC 6455 3.): " + s);
+        }
+        String fragment = uri.getFragment();
+        if (fragment != null) {
+            throw new IllegalArgumentException(format
+                    ("Fragment not allowed in a WebSocket URI (RFC 6455 3.): '%s'",
+                            fragment));
+        }
+    }
+
+    URI getUri() { return uri; }
+
+    HttpClient getClient() { return client; }
+
+    Map<String, List<String>> getHeaders() {
+        LinkedHashMap<String, List<String>> copy = new LinkedHashMap<>(headers.size());
+        headers.forEach((name, values) -> copy.put(name, new LinkedList<>(values)));
+        return copy;
+    }
+
+    WebSocket.Listener getListener() { return listener; }
+
+    Collection<String> getSubprotocols() {
+        return new ArrayList<>(subprotocols);
+    }
+
+    long getTimeout() { return timeout; }
+
+    TimeUnit getTimeUnit() { return timeUnit; }
+
+    private static Collection<String> checkAndReturnSubprotocols(String mostPreferred,
+                                                                 String... lesserPreferred) {
+        checkSubprotocolSyntax(mostPreferred, "mostPreferred");
+        LinkedHashSet<String> subprotocols = new LinkedHashSet<>(1 + lesserPreferred.length);
+        subprotocols.add(mostPreferred);
+        for (int i = 0; i < lesserPreferred.length; i++) {
+            String p = lesserPreferred[i];
+            String location = format("lesserPreferred[%s]", i);
+            requireNonNull(p, location);
+            checkSubprotocolSyntax(p, location);
+            if (!subprotocols.add(p)) {
+                throw new IllegalArgumentException(format(
+                        "Duplicate subprotocols (RFC 6455 4.1.): '%s'", p));
+            }
+        }
+        return subprotocols;
+    }
+
+    private static void checkSubprotocolSyntax(String subprotocol, String location) {
+        if (subprotocol.isEmpty()) {
+            throw new IllegalArgumentException
+                    ("Subprotocol name is empty (RFC 6455 4.1.): " + location);
+        }
+        if (!subprotocol.chars().allMatch(c -> 0x21 <= c && c <= 0x7e)) {
+            throw new IllegalArgumentException
+                    ("Subprotocol name contains illegal characters (RFC 6455 4.1.): "
+                            + location);
+        }
+    }
+}