--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/java.net.http/share/classes/java/net/http/internal/websocket/BuilderImpl.java	Wed Feb 07 14:17:24 2018 +0000
@@ -0,0 +1,149 @@
+/*
+ * Copyright (c) 2015, 2018, 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.internal.websocket;
+
+import java.net.http.HttpClient;
+import java.net.http.WebSocket;
+import java.net.http.WebSocket.Builder;
+import java.net.http.WebSocket.Listener;
+import java.net.http.internal.common.Pair;
+
+import java.net.ProxySelector;
+import java.net.URI;
+import java.time.Duration;
+import java.util.Collection;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Optional;
+import java.util.concurrent.CompletableFuture;
+
+import static java.util.Objects.requireNonNull;
+import static java.net.http.internal.common.Pair.pair;
+
+public final class BuilderImpl implements Builder {
+
+    private final HttpClient client;
+    private URI uri;
+    private Listener listener;
+    private final Optional<ProxySelector> proxySelector;
+    private final Collection<Pair<String, String>> headers;
+    private final Collection<String> subprotocols;
+    private Duration timeout;
+
+    public BuilderImpl(HttpClient client, ProxySelector proxySelector)
+    {
+        this(client, null, null, Optional.ofNullable(proxySelector),
+             new LinkedList<>(), new LinkedList<>(), null);
+    }
+
+    private BuilderImpl(HttpClient client,
+                        URI uri,
+                        Listener listener,
+                        Optional<ProxySelector> proxySelector,
+                        Collection<Pair<String, String>> headers,
+                        Collection<String> subprotocols,
+                        Duration timeout) {
+        this.client = client;
+        this.uri = uri;
+        this.listener = listener;
+        this.proxySelector = proxySelector;
+        // If a proxy selector was supplied by the user, it should be present
+        // on the client and should be the same that what we got as an argument
+        assert !client.proxy().isPresent()
+                || client.proxy().equals(proxySelector);
+        this.headers = headers;
+        this.subprotocols = subprotocols;
+        this.timeout = timeout;
+    }
+
+    @Override
+    public Builder header(String name, String value) {
+        requireNonNull(name, "name");
+        requireNonNull(value, "value");
+        headers.add(pair(name, value));
+        return this;
+    }
+
+    @Override
+    public Builder subprotocols(String mostPreferred, String... lesserPreferred)
+    {
+        requireNonNull(mostPreferred, "mostPreferred");
+        requireNonNull(lesserPreferred, "lesserPreferred");
+        List<String> subprotocols = new LinkedList<>();
+        subprotocols.add(mostPreferred);
+        for (int i = 0; i < lesserPreferred.length; i++) {
+            String p = lesserPreferred[i];
+            requireNonNull(p, "lesserPreferred[" + i + "]");
+            subprotocols.add(p);
+        }
+        this.subprotocols.clear();
+        this.subprotocols.addAll(subprotocols);
+        return this;
+    }
+
+    @Override
+    public Builder connectTimeout(Duration timeout) {
+        this.timeout = requireNonNull(timeout, "timeout");
+        return this;
+    }
+
+    @Override
+    public CompletableFuture<WebSocket> buildAsync(URI uri, Listener listener) {
+        this.uri = requireNonNull(uri, "uri");
+        this.listener = requireNonNull(listener, "listener");
+        // A snapshot of builder inaccessible for further modification
+        // from the outside
+        BuilderImpl copy = immutableCopy();
+        return WebSocketImpl.newInstanceAsync(copy);
+    }
+
+    HttpClient getClient() { return client; }
+
+    URI getUri() { return uri; }
+
+    Listener getListener() { return listener; }
+
+    Collection<Pair<String, String>> getHeaders() { return headers; }
+
+    Collection<String> getSubprotocols() { return subprotocols; }
+
+    Duration getConnectTimeout() { return timeout; }
+
+    Optional<ProxySelector> getProxySelector() { return proxySelector; }
+
+    private BuilderImpl immutableCopy() {
+        @SuppressWarnings({"unchecked", "rawtypes"})
+        BuilderImpl copy = new BuilderImpl(
+                client,
+                uri,
+                listener,
+                proxySelector,
+                List.of(this.headers.toArray(new Pair[0])),
+                List.of(this.subprotocols.toArray(new String[0])),
+                timeout);
+        return copy;
+    }
+}