--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/jdk/java/nio/channels/Selector/KeySets.java	Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,173 @@
+/*
+ * Copyright (c) 2003, 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.
+ *
+ * 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.
+ */
+
+/* @test
+ * @bug 4776783 4778091 4778099
+ * @summary Check various properties of key and selected-key sets
+ *
+ * @run main KeySets
+ */
+
+import java.io.*;
+import java.nio.channels.*;
+import java.util.*;
+
+public class KeySets {
+
+    static abstract class Catch {
+        abstract void go() throws Exception;
+        Catch(Class xc) throws Exception {
+            try {
+                go();
+            } catch (Exception x) {
+                if (xc.isInstance(x))
+                    return;
+                throw new Exception("Wrong exception", x);
+            }
+            throw new Exception("Not thrown as expected: " + xc.getName());
+        }
+    }
+
+    // 4776783: Closing a selector should make key sets inaccessible
+    static void testClose() throws Exception {
+
+        final Selector sel = Selector.open();
+        sel.keys();
+        sel.selectedKeys();
+        sel.close();
+
+        new Catch(ClosedSelectorException.class) {
+                void go() throws Exception {
+                    sel.keys();
+                }};
+
+        new Catch(ClosedSelectorException.class) {
+                void go() throws Exception {
+                    sel.selectedKeys();
+                }};
+    }
+
+    static void testNoAddition(final Set s) throws Exception {
+        new Catch(UnsupportedOperationException.class) {
+                void go() throws Exception {
+                    s.add(new Object());
+                }};
+        new Catch(UnsupportedOperationException.class) {
+                void go() throws Exception {
+                    ArrayList al = new ArrayList();
+                    al.add(new Object());
+                    s.addAll(al);
+                }};
+    }
+
+    static interface Adder {
+        void add() throws IOException;
+    }
+
+    static void testNoRemoval(final Set s, final Adder adder)
+        throws Exception
+    {
+        new Catch(UnsupportedOperationException.class) {
+                void go() throws Exception {
+                    adder.add();
+                    s.clear();
+                }};
+        new Catch(UnsupportedOperationException.class) {
+                void go() throws Exception {
+                    adder.add();
+                    Iterator i = s.iterator();
+                    i.next();
+                    i.remove();
+                }};
+        new Catch(UnsupportedOperationException.class) {
+                void go() throws Exception {
+                    adder.add();
+                    s.remove(s.iterator().next());
+                }};
+        new Catch(UnsupportedOperationException.class) {
+                void go() throws Exception {
+                    adder.add();
+                    HashSet hs = new HashSet();
+                    hs.addAll(s);
+                    s.removeAll(hs);
+                }};
+        new Catch(UnsupportedOperationException.class) {
+                void go() throws Exception {
+                    adder.add();
+                    s.retainAll(Collections.EMPTY_SET);
+                }};
+    }
+
+    static SelectionKey reg(Selector sel) throws IOException {
+        DatagramChannel dc = DatagramChannel.open();
+        dc.configureBlocking(false);
+        return dc.register(sel, SelectionKey.OP_WRITE);
+    }
+
+    static void testMutability() throws Exception {
+
+        final Selector sel = Selector.open();
+
+        // 4778091: Selector.keys() should be immutable
+
+        testNoRemoval(sel.keys(), new Adder() {
+                public void add() throws IOException {
+                    reg(sel);
+                }
+            });
+        testNoAddition(sel.keys());
+
+        // 4778099: Selector.selectedKeys() should allow removal but not addition
+
+        sel.select();
+        testNoAddition(sel.selectedKeys());
+        SelectionKey sk = reg(sel);
+        sel.select();
+        int n = sel.selectedKeys().size();
+        sel.selectedKeys().remove(sk);
+        if (sel.selectedKeys().size() != n - 1)
+            throw new Exception("remove failed");
+
+        HashSet hs = new HashSet();
+        hs.add(reg(sel));
+        sel.select();
+        sel.selectedKeys().retainAll(hs);
+        if (sel.selectedKeys().isEmpty())
+            throw new Exception("retainAll failed");
+        sel.selectedKeys().removeAll(hs);
+        if (!sel.selectedKeys().isEmpty())
+            throw new Exception("removeAll failed");
+
+        hs.clear();
+        hs.add(reg(sel));
+        sel.select();
+        sel.selectedKeys().clear();
+        if (!sel.selectedKeys().isEmpty())
+            throw new Exception("clear failed");
+    }
+
+    public static void main(String[] args) throws Exception {
+        testClose();
+        testMutability();
+    }
+}