7014637: Improve behavior of EnumSet Iterator.remove()

Reviewed-by: mduigou, alanb
Contributed-by: NNeil Richards <neil.richards@ngmr.net>

src/share/classes/java/util/JumboEnumSet.java

@@ -138,8 +138,11 @@ class JumboEnumSet<E extends Enum<E>> extends EnumSet<E> {
         public void remove() {
             if (lastReturned == 0)
                 throw new IllegalStateException();
-            elements[lastReturnedIndex] -= lastReturned;
-            size--;
+            final long oldElements = elements[lastReturnedIndex];
+            elements[lastReturnedIndex] &= ~lastReturned;
+            if (oldElements != elements[lastReturnedIndex]) {
+                size--;
+            }
             lastReturned = 0;
         }
     }

src/share/classes/java/util/RegularEnumSet.java

@@ -106,7 +106,7 @@ class RegularEnumSet<E extends Enum<E>> extends EnumSet<E> {
         public void remove() {
             if (lastReturned == 0)
                 throw new IllegalStateException();
-            elements -= lastReturned;
+            elements &= ~lastReturned;
             lastReturned = 0;
         }
     }

test/java/util/EnumSet/LargeEnumIteratorRemoveResilience.java

+/*
+ * Copyright (c) 2011 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.
+ */
+
+/*
+ * Portions Copyright (c) 2011 IBM Corporation
+ */
+
+/*
+ * @test
+ * @bug 7014637
+ * @summary EnumSet's iterator.remove() can be resilient to set's modification.
+ * @author Neil Richards <neil.richards@ngmr.net>, <neil_richards@uk.ibm.com>
+ */
+
+import java.util.EnumSet;
+import java.util.Iterator;
+import java.util.Set;
+
+public class LargeEnumIteratorRemoveResilience {
+    // enum with more than 64 values
+    private static enum LargeEnum {
+        e00, e01, e02, e03, e04, e05, e06, e07,
+        e08, e09, e0A, e0B, e0C, e0D, e0E, e0F,
+        e10, e11, e12, e13, e14, e15, e16, e17,
+        e18, e19, e1A, e1B, e1C, e1D, e1E, e1F,
+        e20, e21, e22, e23, e24, e25, e26, e27,
+        e28, e29, e2A, e2B, e2C, e2D, e2E, e2F,
+        e30, e31, e32, e33, e34, e35, e36, e37,
+        e38, e39, e3A, e3B, e3C, e3D, e3E, e3F,
+        e40, e41, e42, e43, e44, e45, e46, e47,
+        e48, e49, e4A, e4B, e4C, e4D, e4E, e4F,
+    }
+
+    public static void main(final String[] args) throws Exception {
+        final Set<LargeEnum> set = EnumSet.noneOf(LargeEnum.class);
+
+        set.add(LargeEnum.e2D);
+        set.add(LargeEnum.e42);
+
+        final Iterator<LargeEnum> iterator = set.iterator();
+
+        int size = set.size();
+        LargeEnum element = iterator.next();
+
+        iterator.remove();
+        checkSetAfterRemoval(set, size, element);
+
+        size = set.size();
+        element = iterator.next();
+
+        set.remove(element);
+        checkSetAfterRemoval(set, size, element);
+
+        // The Java API declares that the behaviour here - to call
+        // iterator.remove() after the underlying collection has been
+        // modified - is "unspecified".
+        // However, in the case of iterators for EnumSet, it is easy to
+        // implement their remove() operation such that the set is
+        // unmodified if it is called for an element that has already been
+        // removed from the set - this being the naturally "resilient"
+        // behaviour.
+        iterator.remove();
+        checkSetAfterRemoval(set, size, element);
+    }
+
+    private static void checkSetAfterRemoval(final Set<LargeEnum> set,
+            final int origSize, final LargeEnum removedElement)
+            throws Exception {
+        if (set.size() != (origSize - 1)) {
+            throw new Exception("Test FAILED: Unexpected set size after removal; expected '" + (origSize - 1) + "' but found '" + set.size() + "'");
+        }
+        if (set.contains(removedElement)) {
+            throw new Exception("Test FAILED: Element returned from iterator unexpectedly still in set after removal.");
+        }
+    }
+}

test/java/util/EnumSet/SmallEnumIteratorRemoveResilience.java

+/*
+ * Copyright (c) 2011 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.
+ */
+
+/*
+ * Portions Copyright (c) 2011 IBM Corporation
+ */
+
+/*
+ * @test
+ * @bug 7014637
+ * @summary EnumSet's iterator.remove() can be resilient to set's modification.
+ * @author Neil Richards <neil.richards@ngmr.net>, <neil_richards@uk.ibm.com>
+ */
+
+import java.util.EnumSet;
+import java.util.Iterator;
+import java.util.Set;
+
+public class SmallEnumIteratorRemoveResilience {
+    // enum with less than 64 values
+    private static enum SmallEnum { e0, e1, e2 }
+
+    public static void main(final String[] args) throws Exception {
+        final Set<SmallEnum> set = EnumSet.noneOf(SmallEnum.class);
+
+        set.add(SmallEnum.e0);
+        set.add(SmallEnum.e1);
+
+        final Iterator<SmallEnum> iterator = set.iterator();
+
+        int size = set.size();
+        SmallEnum element = iterator.next();
+
+        iterator.remove();
+        checkSetAfterRemoval(set, size, element);
+
+        size = set.size();
+        element = iterator.next();
+
+        set.remove(element);
+        checkSetAfterRemoval(set, size, element);
+
+        // The Java API declares that the behaviour here - to call
+        // iterator.remove() after the underlying collection has been
+        // modified - is "unspecified".
+        // However, in the case of iterators for EnumSet, it is easy to
+        // implement their remove() operation such that the set is
+        // unmodified if it is called for an element that has already been
+        // removed from the set - this being the naturally "resilient"
+        // behaviour.
+        iterator.remove();
+        checkSetAfterRemoval(set, size, element);
+    }
+
+    private static void checkSetAfterRemoval(final Set<SmallEnum> set,
+            final int origSize, final SmallEnum removedElement)
+            throws Exception {
+        if (set.size() != (origSize - 1)) {
+            throw new Exception("Test FAILED: Unexpected set size after removal; expected '" + (origSize - 1) + "' but found '" + set.size() + "'");
+        }
+        if (set.contains(removedElement)) {
+            throw new Exception("Test FAILED: Element returned from iterator unexpectedly still in set after removal.");
+        }
+    }
+}