jdk/test/java/util/NavigableMap/LockStep.java
changeset 2 90ce3da70b43
child 493 b8102e80be10
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/jdk/test/java/util/NavigableMap/LockStep.java	Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,815 @@
+/*
+ * Copyright 2006 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ */
+
+/*
+ * @test
+ * @bug     6420753 6242436
+ * @summary Compare NavigableMap implementations for identical behavior
+ * @author  Martin Buchholz
+ */
+
+import java.io.*;
+import java.util.*;
+import java.util.concurrent.*;
+import static java.util.Collections.*;
+
+@SuppressWarnings("unchecked")
+public class LockStep {
+    static final int DEFAULT_SIZE = 5;
+    static int size;            // Running time is O(size**2)
+
+    static int intArg(String[] args, int i, int defaultValue) {
+        return args.length > i ? Integer.parseInt(args[i]) : defaultValue;
+    }
+
+    // Pass -Dthorough=true for more exhaustive testing
+    static final boolean thorough = Boolean.getBoolean("thorough");
+
+    static boolean maybe(int n) { return rnd.nextInt(n) == 0; }
+
+    static void realMain(String[] args) {
+        size = intArg(args, 0, DEFAULT_SIZE);
+
+        lockSteps(new TreeMap(),
+                  new ConcurrentSkipListMap());
+        lockSteps(new TreeMap(reverseOrder()),
+                  new ConcurrentSkipListMap(reverseOrder()));
+
+        lockSteps(new TreeSet(),
+                  new ConcurrentSkipListSet());
+        lockSteps(new TreeSet(reverseOrder()),
+                  new ConcurrentSkipListSet(reverseOrder()));
+    }
+
+    static void lockSteps(NavigableMap m1, NavigableMap m2) {
+        if (maybe(4)) m1 = serialClone(m1);
+        if (maybe(4)) m2 = serialClone(m2);
+        lockStep(m1,
+                 m2);
+        lockStep(m1.descendingMap(),
+                 m2.descendingMap());
+        lockStep(fullSubMap(m1),
+                 fullSubMap(m2));
+        lockStep(fullSubMap(m1.descendingMap()),
+                 fullSubMap(m2.descendingMap()));
+        lockStep(fullHeadMap(m1),
+                 fullHeadMap(m2));
+        lockStep(fullHeadMap(m1.descendingMap()),
+                 fullHeadMap(m2.descendingMap()));
+        lockStep(fullTailMap(m1),
+                 fullTailMap(m2));
+        lockStep(fullTailMap(m1.descendingMap()),
+                 fullTailMap(m2.descendingMap()));
+    }
+
+    static void lockSteps(NavigableSet s1, NavigableSet s2) {
+        if (maybe(4)) s1 = serialClone(s1);
+        if (maybe(4)) s2 = serialClone(s2);
+        lockStep(s1,
+                 s2);
+        lockStep(s1.descendingSet(),
+                 s2.descendingSet());
+        lockStep(fullSubSet(s1),
+                 fullSubSet(s2));
+        lockStep(fullSubSet(s1.descendingSet()),
+                 fullSubSet(s2.descendingSet()));
+        lockStep(fullHeadSet(s1),
+                 fullHeadSet(s2));
+        lockStep(fullHeadSet(s1.descendingSet()),
+                 fullHeadSet(s2.descendingSet()));
+        lockStep(fullTailSet(s1),
+                 fullTailSet(s2));
+        lockStep(fullTailSet(s1.descendingSet()),
+                 fullTailSet(s2.descendingSet()));
+    }
+
+    static boolean isAscending(NavigableMap m) {
+        Comparator cmp = m.comparator();
+        return (cmp == null || cmp.compare(1, 2) < 0);
+    }
+
+    static NavigableMap fullSubMap(NavigableMap m) {
+        return isAscending(m)
+            ? m.subMap(Integer.MIN_VALUE, true, Integer.MAX_VALUE, true)
+            : m.subMap(Integer.MAX_VALUE, true, Integer.MIN_VALUE, true);
+    }
+
+    static NavigableMap fullHeadMap(NavigableMap m) {
+        return isAscending(m)
+            ? m.headMap(Integer.MAX_VALUE, true)
+            : m.headMap(Integer.MIN_VALUE, true);
+    }
+
+    static NavigableMap fullTailMap(NavigableMap m) {
+        return isAscending(m)
+            ? m.tailMap(Integer.MIN_VALUE, true)
+            : m.tailMap(Integer.MAX_VALUE, true);
+    }
+
+    static boolean isAscending(NavigableSet s) {
+        Comparator cmp = s.comparator();
+        return (cmp == null || cmp.compare(1, 2) < 0);
+    }
+
+    static NavigableSet fullSubSet(NavigableSet s) {
+        return isAscending(s)
+            ? s.subSet(Integer.MIN_VALUE, true, Integer.MAX_VALUE, true)
+            : s.subSet(Integer.MAX_VALUE, true, Integer.MIN_VALUE, true);
+    }
+
+    static NavigableSet fullHeadSet(NavigableSet s) {
+        return isAscending(s)
+            ? s.headSet(Integer.MAX_VALUE, true)
+            : s.headSet(Integer.MIN_VALUE, true);
+    }
+
+    static NavigableSet fullTailSet(NavigableSet s) {
+        return isAscending(s)
+            ? s.tailSet(Integer.MIN_VALUE, true)
+            : s.tailSet(Integer.MAX_VALUE, true);
+    }
+
+    static void testEmptyCollection(Collection<?> c) {
+        check(c.isEmpty());
+        equal(c.size(), 0);
+        equal(c.toString(),"[]");
+        equal(c.toArray().length, 0);
+        equal(c.toArray(new Object[0]).length, 0);
+
+        Object[] a = new Object[1]; a[0] = Boolean.TRUE;
+        equal(c.toArray(a), a);
+        equal(a[0], null);
+    }
+
+    static void testEmptySet(Set<?> c) {
+        testEmptyCollection(c);
+        equal(c.hashCode(), 0);
+        equal2(c, Collections.<Integer>emptySet());
+    }
+
+    static void testEmptyMap(final Map<?,?> m) {
+        check(m.isEmpty());
+        equal(m.size(), 0);
+        equal(m.toString(),"{}");
+        equal(m.hashCode(), 0);
+        testEmptySet(m.keySet());
+        testEmptySet(m.entrySet());
+        testEmptyCollection(m.values());
+    }
+
+    static final Random rnd = new Random();
+
+    static void equalNext(final Iterator<?> it, Object expected) {
+        if (maybe(2))
+            check(it.hasNext());
+        equal(it.next(), expected);
+    }
+
+    static Comparator comparator(NavigableSet s) {
+        Comparator cmp = s.comparator();
+        return cmp != null ? cmp : new Comparator() {
+            public int compare(Object o1, Object o2) {
+                return ((Comparable) o1).compareTo(o2); }};
+    }
+
+    static Comparator comparator(NavigableMap m) {
+        Comparator cmp = m.comparator();
+        return cmp != null ? cmp : new Comparator() {
+            public int compare(Object o1, Object o2) {
+                return ((Comparable) o1).compareTo(o2); }};
+    }
+
+    static void checkNavigableSet(final NavigableSet s) {
+        if (s.comparator() == null)
+            check(s.descendingSet().descendingSet().comparator() == null);
+        equal(s.isEmpty(), s.size() == 0);
+        equal2(s, s.descendingSet());
+        if (maybe(4) && s instanceof Serializable)
+            equal2(s, serialClone(s));
+        Comparator cmp = comparator(s);
+        if (s.isEmpty()) {
+            THROWS(NoSuchElementException.class,
+                   new Fun(){void f(){ s.first(); }},
+                   new Fun(){void f(){ s.last();  }});
+            equal(null, s.lower(1));
+            equal(null, s.floor(1));
+            equal(null, s.ceiling(1));
+            equal(null, s.higher(1));
+        } else {
+            Object a = s.first();
+            Object z = s.last();
+            equal(s.lower(a), null);
+            equal(s.higher(z), null);
+            equal2(s, s.tailSet(a));
+            equal2(s, s.headSet(z, true));
+            equal2(s, s.subSet(a, true, z, true));
+
+            testEmptySet(s.subSet(a, true, a, false));
+            testEmptySet(s.subSet(z, true, z, false));
+            testEmptySet(s.headSet(a, false));
+            testEmptySet(s.tailSet(z, false));
+
+            equal2(s.headSet(a, true), singleton(a));
+            equal2(s.tailSet(z, true), singleton(z));
+        }
+        Iterator[] its = new Iterator[] {
+            s.iterator(),
+            s.descendingSet().descendingSet().iterator(),
+        };
+        for (final Iterator it : its)
+            if (maybe(4))
+                THROWS(IllegalStateException.class,
+                       new Fun(){void f(){ it.remove(); }});
+        Object prev = null;
+        for (Object e : s) {
+            check(s.contains(e));
+            for (Iterator it : its) equalNext(it, e);
+            equal(e, s.ceiling(e));
+            equal(e, s.floor(e));
+            check(s.higher(e) == null || cmp.compare(e, s.higher(e)) < 0);
+            equal(s.lower(e), prev);
+            if (prev == null) {
+            } else {
+                check(cmp.compare(prev, e) < 0);
+            }
+            prev = e;
+        }
+        for (final Iterator it : its) {
+            if (maybe(2))
+                check(! it.hasNext());
+            Fun fun = new Fun(){void f(){ it.next(); }};
+            THROWS(NoSuchElementException.class, fun, fun, fun);
+        }
+    }
+
+    static void equalNavigableSetsLeaf(final NavigableSet s1,
+                                       final NavigableSet s2) {
+        equal2(s1,            s2);
+        equal( s1.size(),     s2.size());
+        equal( s1.isEmpty(),  s2.isEmpty());
+        equal( s1.hashCode(), s2.hashCode());
+        equal( s1.toString(), s2.toString());
+        if (! s1.isEmpty()) {
+            equal(s1.first(), s2.first());
+            equal(s1.last(),  s2.last());
+        }
+        checkNavigableSet(s1);
+        checkNavigableSet(s2);
+    }
+
+    static void equalNavigableSets(final NavigableSet s1,
+                                   final NavigableSet s2) {
+        equalNavigableSetsLeaf(s1, s2);
+        equalNavigableSetsLeaf(s1.descendingSet(), s2.descendingSet());
+        equalNavigableSetsLeaf(s1.descendingSet().descendingSet(), s2);
+        Object min = s1.isEmpty() ? Integer.MIN_VALUE : s1.first();
+        Object max = s2.isEmpty() ? Integer.MAX_VALUE : s2.last();
+        if (s1.comparator() != null &&
+            s1.comparator().compare(min, max) > 0) {
+            Object tmp = min; min = max; max = tmp;
+        }
+
+        equalNavigableSetsLeaf(s1.subSet(min, true, max, true),
+                               s2.subSet(min, true, max, true));
+        equalNavigableSetsLeaf(s1.tailSet(min, true),
+                               s2.tailSet(min, true));
+        equalNavigableSetsLeaf(s1.headSet(max, true),
+                               s2.headSet(max, true));
+        equalNavigableSetsLeaf((NavigableSet) s1.subSet(min, max),
+                               (NavigableSet) s2.subSet(min, max));
+        equalNavigableSetsLeaf((NavigableSet) s1.tailSet(min),
+                               (NavigableSet) s2.tailSet(min));
+        equalNavigableSetsLeaf((NavigableSet) s1.headSet(max),
+                               (NavigableSet) s2.headSet(max));
+    }
+
+    // Destined for a Collections.java near you?
+    static <T> T[] concat(T[]... arrays) {
+        int len = 0;
+        for (int i = 0; i < arrays.length; i++)
+            len += arrays[i].length;
+        T[] a = (T[])java.lang.reflect.Array
+            .newInstance(arrays[0].getClass().getComponentType(), len);
+        int k = 0;
+        for (int i = 0; i < arrays.length; i++) {
+            T[] array = arrays[i];
+            System.arraycopy(array, 0, a, k, array.length);
+            k += array.length;
+        }
+        return a;
+    }
+
+    static void checkNavigableMap(final NavigableMap m) {
+        if (m.comparator() == null) {
+            check(m.descendingMap().descendingMap().comparator() == null);
+            check(m.descendingKeySet().descendingSet().comparator() == null);
+        }
+        equal(m.isEmpty(), m.size() == 0);
+        equal2(m, m.descendingMap());
+        if (maybe(4))
+            equal2(m, serialClone(m));
+        equal2(m.keySet(), m.descendingKeySet());
+        Comparator cmp = comparator(m);
+        if (m.isEmpty()) {
+            THROWS(NoSuchElementException.class,
+                   new Fun(){void f(){ m.firstKey(); }},
+                   new Fun(){void f(){ m.lastKey();  }});
+            equal(null, m.firstEntry());
+            equal(null, m.lastEntry());
+            equal(null, m.pollFirstEntry());
+            equal(null, m.pollLastEntry());
+            equal(null, m.lowerKey(1));
+            equal(null, m.floorKey(1));
+            equal(null, m.ceilingKey(1));
+            equal(null, m.higherKey(1));
+            equal(null, m.lowerEntry(1));
+            equal(null, m.floorEntry(1));
+            equal(null, m.ceilingEntry(1));
+            equal(null, m.higherEntry(1));
+        } else {
+            Object a = m.firstKey();
+            Object z = m.lastKey();
+            equal(m.lowerKey(a), null);
+            equal(m.higherKey(z), null);
+            equal(a, m.firstEntry().getKey());
+            equal(z, m.lastEntry().getKey());
+            equal2(m, m.tailMap(a));
+            equal2(m, m.headMap(z, true));
+            equal2(m, m.subMap(a, true, z, true));
+
+            testEmptyMap(m.subMap(a, true, a, false));
+            testEmptyMap(m.subMap(z, true, z, false));
+            testEmptyMap(m.headMap(a, false));
+            testEmptyMap(m.tailMap(z, false));
+
+            equal2(m.headMap(a, true), singletonMap(a, m.get(a)));
+            equal2(m.tailMap(z, true), singletonMap(z, m.get(z)));
+        }
+
+        Iterator[] kits = new Iterator[] {
+            m.keySet().iterator(),
+            m.descendingMap().descendingKeySet().iterator(),
+            m.descendingKeySet().descendingSet().iterator(),
+        };
+        Iterator[] vits = new Iterator[] {
+            m.values().iterator(),
+            m.descendingMap().descendingMap().values().iterator(),
+        };
+        Iterator[] eits = new Iterator[] {
+            m.entrySet().iterator(),
+            m.descendingMap().descendingMap().entrySet().iterator(),
+        };
+        Iterator[] its = concat(kits, vits, eits);
+        for (final Iterator it : its)
+            if (maybe(4))
+                THROWS(IllegalStateException.class,
+                       new Fun(){void f(){ it.remove(); }});
+        Map.Entry prev = null;
+        for (Map.Entry e : (Set<Map.Entry>) m.entrySet()) {
+            Object k = e.getKey();
+            Object v = e.getValue();
+            check(m.containsKey(k));
+            check(m.containsValue(v));
+            for (Iterator kit : kits) equalNext(kit, k);
+            for (Iterator vit : vits) equalNext(vit, v);
+            for (Iterator eit : eits) equalNext(eit, e);
+            equal(k, m.ceilingKey(k));
+            equal(k, m.ceilingEntry(k).getKey());
+            equal(k, m.floorKey(k));
+            equal(k, m.floorEntry(k).getKey());
+            check(m.higherKey(k) == null || cmp.compare(k, m.higherKey(k)) < 0);
+            check(m.lowerKey(k)  == null || cmp.compare(k, m.lowerKey(k))  > 0);
+            equal(m.lowerEntry(k), prev);
+            if (prev == null) {
+                equal(m.lowerKey(k), null);
+            } else {
+                equal(m.lowerKey(k), prev.getKey());
+                check(cmp.compare(prev.getKey(), e.getKey()) < 0);
+            }
+            prev = e;
+        }
+        for (final Iterator it : its) {
+            if (maybe(2))
+                check(! it.hasNext());
+            Fun fun = new Fun(){void f(){ it.next(); }};
+            THROWS(NoSuchElementException.class, fun, fun, fun);
+        }
+    }
+
+    static void equalNavigableMapsLeaf(final NavigableMap m1,
+                                       final NavigableMap m2) {
+        equal2(m1,              m2);
+        equal( m1.size(),       m2.size());
+        equal( m1.isEmpty(),    m2.isEmpty());
+        equal( m1.hashCode(),   m2.hashCode());
+        equal( m1.toString(),   m2.toString());
+        equal2(m1.firstEntry(), m2.firstEntry());
+        equal2(m1.lastEntry(),  m2.lastEntry());
+        checkNavigableMap(m1);
+        checkNavigableMap(m2);
+    }
+
+    static void equalNavigableMaps(NavigableMap m1,
+                                   NavigableMap m2) {
+        equalNavigableMapsLeaf(m1, m2);
+        equalNavigableSetsLeaf((NavigableSet) m1.keySet(),
+                               (NavigableSet) m2.keySet());
+        equalNavigableSets(m1.navigableKeySet(),
+                           m2.navigableKeySet());
+        equalNavigableSets(m1.descendingKeySet(),
+                           m2.descendingKeySet());
+        equal2(m1.entrySet(),
+               m2.entrySet());
+        equalNavigableMapsLeaf(m1.descendingMap(),
+                               m2.descendingMap());
+        equalNavigableMapsLeaf(m1.descendingMap().descendingMap(),
+                               m2);
+        equalNavigableSetsLeaf((NavigableSet) m1.descendingMap().keySet(),
+                               (NavigableSet) m2.descendingMap().keySet());
+        equalNavigableSetsLeaf(m1.descendingMap().descendingKeySet(),
+                               m2.descendingMap().descendingKeySet());
+        equal2(m1.descendingMap().entrySet(),
+               m2.descendingMap().entrySet());
+
+        //----------------------------------------------------------------
+        // submaps
+        //----------------------------------------------------------------
+        Object min = Integer.MIN_VALUE;
+        Object max = Integer.MAX_VALUE;
+        if (m1.comparator() != null
+            && m1.comparator().compare(min, max) > 0) {
+            Object tmp = min; min = max; max = tmp;
+        }
+        switch (rnd.nextInt(6)) {
+        case 0:
+            equalNavigableMapsLeaf(m1.subMap(min, true, max, true),
+                                   m2.subMap(min, true, max, true));
+            break;
+        case 1:
+            equalNavigableMapsLeaf(m1.tailMap(min, true),
+                                   m2.tailMap(min, true));
+            break;
+        case 2:
+            equalNavigableMapsLeaf(m1.headMap(max, true),
+                                   m2.headMap(max, true));
+            break;
+        case 3:
+            equalNavigableMapsLeaf((NavigableMap) m1.subMap(min, max),
+                                   (NavigableMap) m2.subMap(min, max));
+            break;
+        case 4:
+            equalNavigableMapsLeaf((NavigableMap) m1.tailMap(min),
+                                   (NavigableMap) m2.tailMap(min));
+            break;
+        case 5:
+            equalNavigableMapsLeaf((NavigableMap) m1.headMap(max),
+                                   (NavigableMap) m2.headMap(max));
+            break;
+        }
+    }
+
+    static abstract class MapFrobber { abstract void frob(NavigableMap m); }
+    static abstract class SetFrobber { abstract void frob(NavigableSet m); }
+
+    static MapFrobber randomAdder(NavigableMap m) {
+        final Integer k = unusedKey(m);
+        MapFrobber f;
+        switch (rnd.nextInt(4)) {
+        case 0: f = new MapFrobber() {void frob(NavigableMap m) {
+            equal(m.put(k, k+1), null);
+            equal(m.get(k), k+1);
+            if (maybe(4)) {
+                equal(m.put(k, k+1), k+1);
+                equal(m.get(k), k+1);}}};
+            break;
+        case 1: f = new MapFrobber() {void frob(NavigableMap m) {
+            m.descendingMap().put(k, k+1);
+            equal(m.get(k), k+1);}};
+            break;
+        case 2: f = new MapFrobber() {void frob(NavigableMap m) {
+            m.tailMap(k,true).headMap(k,true).put(k,k+1);}};
+            break;
+        case 3: f = new MapFrobber() {void frob(NavigableMap m) {
+            m.tailMap(k,true).headMap(k,true).descendingMap().put(k,k+1);}};
+            break;
+        default: throw new Error();
+        }
+        final MapFrobber ff = f;
+        return new MapFrobber() {void frob(NavigableMap m) {
+            ff.frob(m);
+            if (maybe(2)) equal(m.get(k), k+1);
+            if (maybe(4)) {
+                equal(m.put(k, k+1), k+1);
+                equal(m.get(k), k+1);}}};
+    }
+
+    static SetFrobber randomAdder(NavigableSet s) {
+        final Integer e = unusedElt(s);
+        SetFrobber f;
+        switch (rnd.nextInt(4)) {
+        case 0: f = new SetFrobber() {void frob(NavigableSet s) {
+            check(s.add(e));}};
+            break;
+        case 1: f = new SetFrobber() {void frob(NavigableSet s) {
+            s.descendingSet().add(e);}};
+            break;
+        case 2: f = new SetFrobber() {void frob(NavigableSet s) {
+            s.tailSet(e,true).headSet(e,true).add(e);}};
+            break;
+        case 3: f = new SetFrobber() {void frob(NavigableSet s) {
+            s.descendingSet().tailSet(e,true).headSet(e,true).add(e);}};
+            break;
+        default: throw new Error();
+        }
+        final SetFrobber ff = f;
+        return new SetFrobber() {void frob(NavigableSet s) {
+            if (maybe(2)) check(! s.contains(e));
+            ff.frob(s);
+            if (maybe(2)) check(! s.add(e));
+            if (maybe(2)) check(s.contains(e));}};
+    }
+
+    static Integer unusedElt(NavigableSet s) {
+        Integer e;
+        do { e = rnd.nextInt(1024); }
+        while (s.contains(e));
+        return e;
+    }
+
+    static Integer unusedKey(NavigableMap m) {
+        Integer k;
+        do { k = rnd.nextInt(1024); }
+        while (m.containsKey(k));
+        return k;
+    }
+
+    static Integer usedKey(NavigableMap m) {
+        Integer x = rnd.nextInt(1024);
+        Integer floor   = (Integer) m.floorKey(x);
+        Integer ceiling = (Integer) m.ceilingKey(x);
+        if (floor != null) return floor;
+        check(ceiling != null);
+        return ceiling;
+    }
+
+    static Integer usedElt(NavigableSet s) {
+        Integer x = rnd.nextInt(1024);
+        Integer floor   = (Integer) s.floor(x);
+        Integer ceiling = (Integer) s.ceiling(x);
+        if (floor != null) return floor;
+        check(ceiling != null);
+        return ceiling;
+    }
+
+    static void checkUnusedKey(NavigableMap m, Object k) {
+        check(! m.containsKey(k));
+        equal(m.get(k), null);
+        if (maybe(2))
+            equal(m.remove(k), null);
+    }
+
+    static void checkUnusedElt(NavigableSet s, Object e) {
+        if (maybe(2))
+            check(! s.contains(e));
+        if (maybe(2)) {
+            check(s.ceiling(e) != e);
+            check(s.floor(e)   != e);
+        }
+        if (maybe(2))
+            check(! s.remove(e));
+    }
+
+    static Fun remover(final Iterator it) {
+        return new Fun(){void f(){ it.remove(); }};
+    }
+
+    static MapFrobber randomRemover(NavigableMap m) {
+        final Integer k = usedKey(m);
+        switch (rnd.nextInt(7)) {
+        default: throw new Error();
+        case 0: return new MapFrobber() {void frob(NavigableMap m) {
+            Map.Entry e = m.firstEntry();
+            equal(m.pollFirstEntry(), e);
+            checkUnusedKey(m, e.getKey());}};
+        case 1: return new MapFrobber() {void frob(NavigableMap m) {
+            Map.Entry e = m.lastEntry();
+            equal(m.pollLastEntry(), e);
+            checkUnusedKey(m, e.getKey());}};
+        case 2: return new MapFrobber() {void frob(NavigableMap m) {
+            check(m.remove(k) != null);
+            checkUnusedKey(m, k);}};
+        case 3: return new MapFrobber() {void frob(NavigableMap m) {
+            m.subMap(k, true, k, true).clear();
+            checkUnusedKey(m, k);}};
+        case 4: return new MapFrobber() {void frob(NavigableMap m) {
+            m.descendingMap().subMap(k, true, k, true).clear();
+            checkUnusedKey(m, k);}};
+        case 5: return new MapFrobber() {void frob(NavigableMap m) {
+            final Iterator it = m.keySet().iterator();
+            while (it.hasNext())
+                if (it.next().equals(k)) {
+                    it.remove();
+                    if (maybe(2))
+                        THROWS(IllegalStateException.class,
+                               new Fun(){void f(){ it.remove(); }});
+                }
+            checkUnusedKey(m, k);}};
+        case 6: return new MapFrobber() {void frob(NavigableMap m) {
+            final Iterator<Map.Entry> it = m.entrySet().iterator();
+            while (it.hasNext())
+                if (it.next().getKey().equals(k)) {
+                    it.remove();
+                    if (maybe(2))
+                        THROWS(IllegalStateException.class, remover(it));
+                }
+            checkUnusedKey(m, k);}};
+        }
+    }
+
+    static SetFrobber randomRemover(NavigableSet s) {
+        final Integer e = usedElt(s);
+        switch (rnd.nextInt(7)) {
+        default: throw new Error();
+        case 0: return new SetFrobber() {void frob(NavigableSet s) {
+            Object e = s.first();
+            equal(s.pollFirst(), e);
+            checkUnusedElt(s, e);}};
+        case 1: return new SetFrobber() {void frob(NavigableSet s) {
+            Object e = s.last();
+            equal(s.pollLast(), e);
+            checkUnusedElt(s, e);}};
+        case 2: return new SetFrobber() {void frob(NavigableSet s) {
+            check(s.remove(e));
+            checkUnusedElt(s, e);}};
+        case 3: return new SetFrobber() {void frob(NavigableSet s) {
+            s.subSet(e, true, e, true).clear();
+            checkUnusedElt(s, e);}};
+        case 4: return new SetFrobber() {void frob(NavigableSet s) {
+            s.descendingSet().subSet(e, true, e, true).clear();
+            checkUnusedElt(s, e);}};
+        case 5: return new SetFrobber() {void frob(NavigableSet s) {
+            final Iterator it = s.iterator();
+            while (it.hasNext())
+                if (it.next().equals(e)) {
+                    it.remove();
+                    if (maybe(2))
+                        THROWS(IllegalStateException.class,
+                               new Fun(){void f(){ it.remove(); }});
+                }
+            checkUnusedElt(s, e);}};
+        case 6: return new SetFrobber() {void frob(NavigableSet s) {
+            final Iterator it = s.descendingSet().iterator();
+            while (it.hasNext())
+                if (it.next().equals(e)) {
+                    it.remove();
+                    if (maybe(2))
+                        THROWS(IllegalStateException.class,
+                               new Fun(){void f(){ it.remove(); }});
+                }
+            checkUnusedElt(s, e);}};
+        }
+    }
+
+    static void lockStep(NavigableMap m1,
+                         NavigableMap m2) {
+        if (! (thorough || maybe(3))) return;
+        if (maybe(4)) m1 = serialClone(m1);
+        if (maybe(4)) m2 = serialClone(m2);
+
+        List<NavigableMap> maps = Arrays.asList(m1, m2);
+        for (NavigableMap m : maps) testEmptyMap(m);
+        final Set<Integer> ints = new HashSet<Integer>();
+        while (ints.size() < size)
+            ints.add(rnd.nextInt(1024));
+        final Integer[] elts = ints.toArray(new Integer[size]);
+        for (int i = 0; i < size; i++) {
+            MapFrobber adder = randomAdder(m1);
+            for (final NavigableMap m : maps) {
+                adder.frob(m);
+                equal(m.size(), i+1);
+            }
+            equalNavigableMaps(m1, m2);
+        }
+        for (final NavigableMap m : maps) {
+            final Object e = usedKey(m);
+            THROWS(IllegalArgumentException.class,
+                   new Fun(){void f(){m.subMap(e,true,e,false)
+                                       .subMap(e,true,e,true);}},
+                   new Fun(){void f(){m.subMap(e,false,e,true)
+                                       .subMap(e,true,e,true);}},
+                   new Fun(){void f(){m.tailMap(e,false).tailMap(e,true);}},
+                   new Fun(){void f(){m.headMap(e,false).headMap(e,true);}});
+        }
+        //System.out.printf("%s%n", m1);
+        for (int i = size; i > 0; i--) {
+            MapFrobber remover = randomRemover(m1);
+            for (final NavigableMap m : maps) {
+                remover.frob(m);
+                equal(m.size(), i-1);
+            }
+            equalNavigableMaps(m1, m2);
+        }
+        for (NavigableMap m : maps) testEmptyMap(m);
+    }
+
+    static void lockStep(NavigableSet s1,
+                         NavigableSet s2) {
+        if (! (thorough || maybe(3))) return;
+        if (maybe(4)) s1 = serialClone(s1);
+        if (maybe(4)) s2 = serialClone(s2);
+
+        List<NavigableSet> sets = Arrays.asList(s1, s2);
+        for (NavigableSet s : sets) testEmptySet(s);
+        final Set<Integer> ints = new HashSet<Integer>();
+        while (ints.size() < size)
+            ints.add(rnd.nextInt(1024));
+        final Integer[] elts = ints.toArray(new Integer[size]);
+        for (int i = 0; i < size; i++) {
+            SetFrobber adder = randomAdder(s1);
+            for (final NavigableSet s : sets) {
+                adder.frob(s);
+                equal(s.size(), i+1);
+            }
+            equalNavigableSets(s1, s2);
+        }
+        for (final NavigableSet s : sets) {
+            final Object e = usedElt(s);
+            THROWS(IllegalArgumentException.class,
+                   new Fun(){void f(){s.subSet(e,true,e,false)
+                                       .subSet(e,true,e,true);}},
+                   new Fun(){void f(){s.subSet(e,false,e,true)
+                                       .subSet(e,true,e,true);}},
+                   new Fun(){void f(){s.tailSet(e,false).tailSet(e,true);}},
+                   new Fun(){void f(){s.headSet(e,false).headSet(e,true);}});
+        }
+        //System.out.printf("%s%n", s1);
+        for (int i = size; i > 0; i--) {
+            SetFrobber remover = randomRemover(s1);
+            for (final NavigableSet s : sets) {
+                remover.frob(s);
+                equal(s.size(), i-1);
+            }
+            equalNavigableSets(s1, s2);
+        }
+        for (NavigableSet s : sets) testEmptySet(s);
+    }
+
+    //--------------------- Infrastructure ---------------------------
+    static volatile int passed = 0, failed = 0;
+    static void pass() { passed++; }
+    static void fail() { failed++; Thread.dumpStack(); }
+    static void fail(String msg) { System.out.println(msg); fail(); }
+    static void unexpected(Throwable t) { failed++; t.printStackTrace(); }
+    static void check(boolean cond) { if (cond) pass(); else fail(); }
+    static void equal(Object x, Object y) {
+        if (x == null ? y == null : x.equals(y)) pass();
+        else {System.out.println(x + " not equal to " + y); fail();}}
+    static void equal2(Object x, Object y) {equal(x, y); equal(y, x);}
+    public static void main(String[] args) throws Throwable {
+        try { realMain(args); } catch (Throwable t) { unexpected(t); }
+
+        System.out.printf("%nPassed = %d, failed = %d%n%n", passed, failed);
+        if (failed > 0) throw new Exception("Some tests failed");
+    }
+    static abstract class Fun {abstract void f() throws Throwable;}
+    static void THROWS(Class<? extends Throwable> k, Fun... fs) {
+          for (Fun f : fs)
+              try { f.f(); fail("Expected " + k.getName() + " not thrown"); }
+              catch (Throwable t) {
+                  if (k.isAssignableFrom(t.getClass())) pass();
+                  else unexpected(t);}}
+    static byte[] serializedForm(Object obj) {
+        try {
+            ByteArrayOutputStream baos = new ByteArrayOutputStream();
+            new ObjectOutputStream(baos).writeObject(obj);
+            return baos.toByteArray();
+        } catch (IOException e) { throw new RuntimeException(e); }}
+    static Object readObject(byte[] bytes)
+        throws IOException, ClassNotFoundException {
+        InputStream is = new ByteArrayInputStream(bytes);
+        return new ObjectInputStream(is).readObject();}
+    @SuppressWarnings("unchecked")
+    static <T> T serialClone(T obj) {
+        try { return (T) readObject(serializedForm(obj)); }
+        catch (Exception e) { throw new RuntimeException(e); }}
+}