--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/java.base/share/classes/jdk/internal/module/DefaultRoots.java	Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,93 @@
+/*
+ * Copyright (c) 2017, 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.module;
+
+import java.lang.module.ModuleDescriptor;
+import java.lang.module.ModuleFinder;
+import java.lang.module.ModuleReference;
+import java.util.HashSet;
+import java.util.Set;
+
+/**
+ * Defines methods to compute the default set of root modules for the unnamed
+ * module.
+ */
+
+public final class DefaultRoots {
+    private static final String JAVA_SE = "java.se";
+
+    private DefaultRoots() { }
+
+    /**
+     * Returns the default set of root modules for the unnamed module computed from
+     * the system modules observable with the given module finder.
+     */
+    static Set<String> compute(ModuleFinder systemModuleFinder, ModuleFinder finder) {
+        Set<String> roots = new HashSet<>();
+
+        boolean hasJava = false;
+        if (systemModuleFinder.find(JAVA_SE).isPresent()) {
+            if (finder == systemModuleFinder || finder.find(JAVA_SE).isPresent()) {
+                // java.se is a system module
+                hasJava = true;
+                roots.add(JAVA_SE);
+            }
+        }
+
+        for (ModuleReference mref : systemModuleFinder.findAll()) {
+            String mn = mref.descriptor().name();
+            if (hasJava && mn.startsWith("java.")) {
+                // not a root
+                continue;
+            }
+
+            if (ModuleResolution.doNotResolveByDefault(mref)) {
+                // not a root
+                continue;
+            }
+
+            if ((finder == systemModuleFinder || finder.find(mn).isPresent())) {
+                // add as root if exports at least one package to all modules
+                ModuleDescriptor descriptor = mref.descriptor();
+                for (ModuleDescriptor.Exports e : descriptor.exports()) {
+                    if (!e.isQualified()) {
+                        roots.add(mn);
+                        break;
+                    }
+                }
+            }
+        }
+
+        return roots;
+    }
+
+    /**
+     * Returns the default set of root modules for the unnamed module from the
+     * modules observable with the given module finder.
+     */
+    public static Set<String> compute(ModuleFinder finder) {
+        return compute(finder, finder);
+    }
+}