--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/java.base/share/classes/jdk/internal/util/jar/VersionedStream.java	Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,85 @@
+/*
+ * Copyright (c) 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 jdk.internal.util.jar;
+
+import java.util.Objects;
+import java.util.jar.JarEntry;
+import java.util.jar.JarFile;
+import java.util.stream.Stream;
+
+public class VersionedStream {
+    private static final String META_INF_VERSIONS = "META-INF/versions/";
+
+    /**
+     * Returns a stream of versioned entries, derived from the base names of
+     * all entries in a multi-release {@code JarFile} that are present either in
+     * the base directory or in any versioned directory with a version number
+     * less than or equal to the {@code Runtime.Version::major} that the
+     * {@code JarFile} was opened with.  These versioned entries are aliases
+     * for the real entries -- i.e. the names are base names and the content
+     * may come from a versioned directory entry.  If the {@code jarFile} is not
+     * a multi-release jar, a stream of all entries is returned.
+     *
+     * @param jf the input JarFile
+     * @return stream of entries
+     * @since 9
+     */
+    public static Stream<JarEntry> stream(JarFile jf) {
+        if (jf.isMultiRelease()) {
+            int version = jf.getVersion().major();
+            return jf.stream()
+                    .map(je -> getBaseSuffix(je, version))
+                    .filter(Objects::nonNull)
+                    .distinct()
+                    .map(jf::getJarEntry);
+        }
+        return jf.stream();
+    }
+
+    private static String getBaseSuffix(JarEntry je, int version) {
+        String name = je.getName();
+        if (name.startsWith(META_INF_VERSIONS)) {
+            int len = META_INF_VERSIONS.length();
+            int index = name.indexOf('/', len);
+            if (index == -1 || index == (name.length() - 1)) {
+                // filter out META-INF/versions/* and META-INF/versions/*/
+                return null;
+            }
+            try {
+                if (Integer.parseInt(name, len, index, 10) > version) {
+                    // not an integer
+                    return null;
+                }
+            } catch (NumberFormatException x) {
+                // silently remove malformed entries
+                return null;
+            }
+            // We know name looks like META-INF/versions/*/*
+            return name.substring(index + 1);
+        }
+        return name;
+    }
+}