diff -r f7fd051519ac -r ee6f7a61f3a5 src/java.net.http/share/classes/jdk/internal/net/http/frame/Http2Frame.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/java.net.http/share/classes/jdk/internal/net/http/frame/Http2Frame.java	Tue Apr 17 08:54:17 2018 -0700
@@ -0,0 +1,141 @@
+/*
+ * 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 jdk.internal.net.http.frame;
+
+/**
+ * When sending a frame, the length field must be set in sub-class
+ * by calling computeLength()
+ */
+public abstract class Http2Frame {
+
+    public static final int FRAME_HEADER_SIZE = 9;
+
+    protected int streamid;
+    protected int flags;
+
+    public Http2Frame(int streamid, int flags) {
+        this.streamid = streamid;
+        this.flags = flags;
+    }
+
+    public int streamid() {
+        return streamid;
+    }
+
+    public void setFlag(int flag) {
+        flags |= flag;
+    }
+
+    public int getFlags() {
+        return flags;
+    }
+
+    public boolean getFlag(int flag) {
+        return (flags & flag) != 0;
+    }
+
+//    public void clearFlag(int flag) {
+//        flags &= 0xffffffff ^ flag;
+//    }
+
+    public void streamid(int streamid) {
+        this.streamid = streamid;
+    }
+
+
+    private String typeAsString() {
+        return asString(type());
+    }
+
+    public int type() {
+        return -1; // Unknown type
+    }
+
+    int length() {
+        return -1; // Unknown length
+    }
+
+
+    public static String asString(int type) {
+        switch (type) {
+          case DataFrame.TYPE:
+            return "DATA";
+          case HeadersFrame.TYPE:
+            return "HEADERS";
+          case ContinuationFrame.TYPE:
+            return "CONTINUATION";
+          case ResetFrame.TYPE:
+            return "RESET";
+          case PriorityFrame.TYPE:
+            return "PRIORITY";
+          case SettingsFrame.TYPE:
+            return "SETTINGS";
+          case GoAwayFrame.TYPE:
+            return "GOAWAY";
+          case PingFrame.TYPE:
+            return "PING";
+          case PushPromiseFrame.TYPE:
+            return "PUSH_PROMISE";
+          case WindowUpdateFrame.TYPE:
+            return "WINDOW_UPDATE";
+          default:
+            return "UNKNOWN";
+        }
+    }
+
+    @Override
+    public String toString() {
+        StringBuilder sb = new StringBuilder();
+        sb.append(typeAsString())
+                .append(": length=")
+                .append(Integer.toString(length()))
+                .append(", streamid=")
+                .append(streamid)
+                .append(", flags=");
+
+        int f = flags;
+        int i = 0;
+        if (f == 0) {
+            sb.append("0 ");
+        } else {
+            while (f != 0) {
+                if ((f & 1) == 1) {
+                    sb.append(flagAsString(1 << i))
+                      .append(' ');
+                }
+                f = f >> 1;
+                i++;
+            }
+        }
+        return sb.toString();
+    }
+
+    // Override
+    public String flagAsString(int f) {
+        return "unknown";
+    }
+
+}