1/*
2 * Written by Doug Lea with assistance from members of JCP JSR-166
3 * Expert Group and released to the public domain, as explained at
4 * http://creativecommons.org/publicdomain/zero/1.0/
5 */
6
7package jsr166;
8
9import junit.framework.*;
10import java.util.Arrays;
11import java.util.BitSet;
12import java.util.Collection;
13import java.util.Comparator;
14import java.util.Iterator;
15import java.util.NavigableSet;
16import java.util.NoSuchElementException;
17import java.util.Random;
18import java.util.Set;
19import java.util.SortedSet;
20import java.util.concurrent.ConcurrentSkipListSet;
21
22public class ConcurrentSkipListSetTest extends JSR166TestCase {
23
24    static class MyReverseComparator implements Comparator {
25        public int compare(Object x, Object y) {
26            return ((Comparable)y).compareTo(x);
27        }
28    }
29
30    /**
31     * Returns a new set of given size containing consecutive
32     * Integers 0 ... n.
33     */
34    private ConcurrentSkipListSet<Integer> populatedSet(int n) {
35        ConcurrentSkipListSet<Integer> q =
36            new ConcurrentSkipListSet<Integer>();
37        assertTrue(q.isEmpty());
38        for (int i = n-1; i >= 0; i-=2)
39            assertTrue(q.add(new Integer(i)));
40        for (int i = (n & 1); i < n; i+=2)
41            assertTrue(q.add(new Integer(i)));
42        assertFalse(q.isEmpty());
43        assertEquals(n, q.size());
44        return q;
45    }
46
47    /**
48     * Returns a new set of first 5 ints.
49     */
50    private ConcurrentSkipListSet set5() {
51        ConcurrentSkipListSet q = new ConcurrentSkipListSet();
52        assertTrue(q.isEmpty());
53        q.add(one);
54        q.add(two);
55        q.add(three);
56        q.add(four);
57        q.add(five);
58        assertEquals(5, q.size());
59        return q;
60    }
61
62    /**
63     * A new set has unbounded capacity
64     */
65    public void testConstructor1() {
66        assertEquals(0, new ConcurrentSkipListSet().size());
67    }
68
69    /**
70     * Initializing from null Collection throws NPE
71     */
72    public void testConstructor3() {
73        try {
74            ConcurrentSkipListSet q = new ConcurrentSkipListSet((Collection)null);
75            shouldThrow();
76        } catch (NullPointerException success) {}
77    }
78
79    /**
80     * Initializing from Collection of null elements throws NPE
81     */
82    public void testConstructor4() {
83        try {
84            Integer[] ints = new Integer[SIZE];
85            ConcurrentSkipListSet q = new ConcurrentSkipListSet(Arrays.asList(ints));
86            shouldThrow();
87        } catch (NullPointerException success) {}
88    }
89
90    /**
91     * Initializing from Collection with some null elements throws NPE
92     */
93    public void testConstructor5() {
94        try {
95            Integer[] ints = new Integer[SIZE];
96            for (int i = 0; i < SIZE-1; ++i)
97                ints[i] = new Integer(i);
98            ConcurrentSkipListSet q = new ConcurrentSkipListSet(Arrays.asList(ints));
99            shouldThrow();
100        } catch (NullPointerException success) {}
101    }
102
103    /**
104     * Set contains all elements of collection used to initialize
105     */
106    public void testConstructor6() {
107        Integer[] ints = new Integer[SIZE];
108        for (int i = 0; i < SIZE; ++i)
109            ints[i] = new Integer(i);
110        ConcurrentSkipListSet q = new ConcurrentSkipListSet(Arrays.asList(ints));
111        for (int i = 0; i < SIZE; ++i)
112            assertEquals(ints[i], q.pollFirst());
113    }
114
115    /**
116     * The comparator used in constructor is used
117     */
118    public void testConstructor7() {
119        MyReverseComparator cmp = new MyReverseComparator();
120        ConcurrentSkipListSet q = new ConcurrentSkipListSet(cmp);
121        assertEquals(cmp, q.comparator());
122        Integer[] ints = new Integer[SIZE];
123        for (int i = 0; i < SIZE; ++i)
124            ints[i] = new Integer(i);
125        q.addAll(Arrays.asList(ints));
126        for (int i = SIZE-1; i >= 0; --i)
127            assertEquals(ints[i], q.pollFirst());
128    }
129
130    /**
131     * isEmpty is true before add, false after
132     */
133    public void testEmpty() {
134        ConcurrentSkipListSet q = new ConcurrentSkipListSet();
135        assertTrue(q.isEmpty());
136        q.add(new Integer(1));
137        assertFalse(q.isEmpty());
138        q.add(new Integer(2));
139        q.pollFirst();
140        q.pollFirst();
141        assertTrue(q.isEmpty());
142    }
143
144    /**
145     * size changes when elements added and removed
146     */
147    public void testSize() {
148        ConcurrentSkipListSet q = populatedSet(SIZE);
149        for (int i = 0; i < SIZE; ++i) {
150            assertEquals(SIZE-i, q.size());
151            q.pollFirst();
152        }
153        for (int i = 0; i < SIZE; ++i) {
154            assertEquals(i, q.size());
155            q.add(new Integer(i));
156        }
157    }
158
159    /**
160     * add(null) throws NPE
161     */
162    public void testAddNull() {
163        try {
164            ConcurrentSkipListSet q = new ConcurrentSkipListSet();
165            q.add(null);
166            shouldThrow();
167        } catch (NullPointerException success) {}
168    }
169
170    /**
171     * Add of comparable element succeeds
172     */
173    public void testAdd() {
174        ConcurrentSkipListSet q = new ConcurrentSkipListSet();
175        assertTrue(q.add(zero));
176        assertTrue(q.add(one));
177    }
178
179    /**
180     * Add of duplicate element fails
181     */
182    public void testAddDup() {
183        ConcurrentSkipListSet q = new ConcurrentSkipListSet();
184        assertTrue(q.add(zero));
185        assertFalse(q.add(zero));
186    }
187
188    /**
189     * Add of non-Comparable throws CCE
190     */
191    public void testAddNonComparable() {
192        try {
193            ConcurrentSkipListSet q = new ConcurrentSkipListSet();
194            q.add(new Object());
195            q.add(new Object());
196            q.add(new Object());
197            shouldThrow();
198        } catch (ClassCastException success) {}
199    }
200
201    /**
202     * addAll(null) throws NPE
203     */
204    public void testAddAll1() {
205        try {
206            ConcurrentSkipListSet q = new ConcurrentSkipListSet();
207            q.addAll(null);
208            shouldThrow();
209        } catch (NullPointerException success) {}
210    }
211
212    /**
213     * addAll of a collection with null elements throws NPE
214     */
215    public void testAddAll2() {
216        try {
217            ConcurrentSkipListSet q = new ConcurrentSkipListSet();
218            Integer[] ints = new Integer[SIZE];
219            q.addAll(Arrays.asList(ints));
220            shouldThrow();
221        } catch (NullPointerException success) {}
222    }
223
224    /**
225     * addAll of a collection with any null elements throws NPE after
226     * possibly adding some elements
227     */
228    public void testAddAll3() {
229        try {
230            ConcurrentSkipListSet q = new ConcurrentSkipListSet();
231            Integer[] ints = new Integer[SIZE];
232            for (int i = 0; i < SIZE-1; ++i)
233                ints[i] = new Integer(i);
234            q.addAll(Arrays.asList(ints));
235            shouldThrow();
236        } catch (NullPointerException success) {}
237    }
238
239    /**
240     * Set contains all elements of successful addAll
241     */
242    public void testAddAll5() {
243        Integer[] empty = new Integer[0];
244        Integer[] ints = new Integer[SIZE];
245        for (int i = 0; i < SIZE; ++i)
246            ints[i] = new Integer(SIZE-1-i);
247        ConcurrentSkipListSet q = new ConcurrentSkipListSet();
248        assertFalse(q.addAll(Arrays.asList(empty)));
249        assertTrue(q.addAll(Arrays.asList(ints)));
250        for (int i = 0; i < SIZE; ++i)
251            assertEquals(i, q.pollFirst());
252    }
253
254    /**
255     * pollFirst succeeds unless empty
256     */
257    public void testPollFirst() {
258        ConcurrentSkipListSet q = populatedSet(SIZE);
259        for (int i = 0; i < SIZE; ++i) {
260            assertEquals(i, q.pollFirst());
261        }
262        assertNull(q.pollFirst());
263    }
264
265    /**
266     * pollLast succeeds unless empty
267     */
268    public void testPollLast() {
269        ConcurrentSkipListSet q = populatedSet(SIZE);
270        for (int i = SIZE-1; i >= 0; --i) {
271            assertEquals(i, q.pollLast());
272        }
273        assertNull(q.pollFirst());
274    }
275
276    /**
277     * remove(x) removes x and returns true if present
278     */
279    public void testRemoveElement() {
280        ConcurrentSkipListSet q = populatedSet(SIZE);
281        for (int i = 1; i < SIZE; i+=2) {
282            assertTrue(q.contains(i));
283            assertTrue(q.remove(i));
284            assertFalse(q.contains(i));
285            assertTrue(q.contains(i-1));
286        }
287        for (int i = 0; i < SIZE; i+=2) {
288            assertTrue(q.contains(i));
289            assertTrue(q.remove(i));
290            assertFalse(q.contains(i));
291            assertFalse(q.remove(i+1));
292            assertFalse(q.contains(i+1));
293        }
294        assertTrue(q.isEmpty());
295    }
296
297    /**
298     * contains(x) reports true when elements added but not yet removed
299     */
300    public void testContains() {
301        ConcurrentSkipListSet q = populatedSet(SIZE);
302        for (int i = 0; i < SIZE; ++i) {
303            assertTrue(q.contains(new Integer(i)));
304            q.pollFirst();
305            assertFalse(q.contains(new Integer(i)));
306        }
307    }
308
309    /**
310     * clear removes all elements
311     */
312    public void testClear() {
313        ConcurrentSkipListSet q = populatedSet(SIZE);
314        q.clear();
315        assertTrue(q.isEmpty());
316        assertEquals(0, q.size());
317        q.add(new Integer(1));
318        assertFalse(q.isEmpty());
319        q.clear();
320        assertTrue(q.isEmpty());
321    }
322
323    /**
324     * containsAll(c) is true when c contains a subset of elements
325     */
326    public void testContainsAll() {
327        ConcurrentSkipListSet q = populatedSet(SIZE);
328        ConcurrentSkipListSet p = new ConcurrentSkipListSet();
329        for (int i = 0; i < SIZE; ++i) {
330            assertTrue(q.containsAll(p));
331            assertFalse(p.containsAll(q));
332            p.add(new Integer(i));
333        }
334        assertTrue(p.containsAll(q));
335    }
336
337    /**
338     * retainAll(c) retains only those elements of c and reports true if changed
339     */
340    public void testRetainAll() {
341        ConcurrentSkipListSet q = populatedSet(SIZE);
342        ConcurrentSkipListSet p = populatedSet(SIZE);
343        for (int i = 0; i < SIZE; ++i) {
344            boolean changed = q.retainAll(p);
345            if (i == 0)
346                assertFalse(changed);
347            else
348                assertTrue(changed);
349
350            assertTrue(q.containsAll(p));
351            assertEquals(SIZE-i, q.size());
352            p.pollFirst();
353        }
354    }
355
356    /**
357     * removeAll(c) removes only those elements of c and reports true if changed
358     */
359    public void testRemoveAll() {
360        for (int i = 1; i < SIZE; ++i) {
361            ConcurrentSkipListSet q = populatedSet(SIZE);
362            ConcurrentSkipListSet p = populatedSet(i);
363            assertTrue(q.removeAll(p));
364            assertEquals(SIZE-i, q.size());
365            for (int j = 0; j < i; ++j) {
366                Integer I = (Integer)(p.pollFirst());
367                assertFalse(q.contains(I));
368            }
369        }
370    }
371
372    /**
373     * lower returns preceding element
374     */
375    public void testLower() {
376        ConcurrentSkipListSet q = set5();
377        Object e1 = q.lower(three);
378        assertEquals(two, e1);
379
380        Object e2 = q.lower(six);
381        assertEquals(five, e2);
382
383        Object e3 = q.lower(one);
384        assertNull(e3);
385
386        Object e4 = q.lower(zero);
387        assertNull(e4);
388    }
389
390    /**
391     * higher returns next element
392     */
393    public void testHigher() {
394        ConcurrentSkipListSet q = set5();
395        Object e1 = q.higher(three);
396        assertEquals(four, e1);
397
398        Object e2 = q.higher(zero);
399        assertEquals(one, e2);
400
401        Object e3 = q.higher(five);
402        assertNull(e3);
403
404        Object e4 = q.higher(six);
405        assertNull(e4);
406    }
407
408    /**
409     * floor returns preceding element
410     */
411    public void testFloor() {
412        ConcurrentSkipListSet q = set5();
413        Object e1 = q.floor(three);
414        assertEquals(three, e1);
415
416        Object e2 = q.floor(six);
417        assertEquals(five, e2);
418
419        Object e3 = q.floor(one);
420        assertEquals(one, e3);
421
422        Object e4 = q.floor(zero);
423        assertNull(e4);
424    }
425
426    /**
427     * ceiling returns next element
428     */
429    public void testCeiling() {
430        ConcurrentSkipListSet q = set5();
431        Object e1 = q.ceiling(three);
432        assertEquals(three, e1);
433
434        Object e2 = q.ceiling(zero);
435        assertEquals(one, e2);
436
437        Object e3 = q.ceiling(five);
438        assertEquals(five, e3);
439
440        Object e4 = q.ceiling(six);
441        assertNull(e4);
442    }
443
444    /**
445     * toArray contains all elements in sorted order
446     */
447    public void testToArray() {
448        ConcurrentSkipListSet q = populatedSet(SIZE);
449        Object[] o = q.toArray();
450        for (int i = 0; i < o.length; i++)
451            assertSame(o[i], q.pollFirst());
452    }
453
454    /**
455     * toArray(a) contains all elements in sorted order
456     */
457    public void testToArray2() {
458        ConcurrentSkipListSet<Integer> q = populatedSet(SIZE);
459        Integer[] ints = new Integer[SIZE];
460        assertSame(ints, q.toArray(ints));
461        for (int i = 0; i < ints.length; i++)
462            assertSame(ints[i], q.pollFirst());
463    }
464
465    /**
466     * iterator iterates through all elements
467     */
468    public void testIterator() {
469        ConcurrentSkipListSet q = populatedSet(SIZE);
470        int i = 0;
471        Iterator it = q.iterator();
472        while (it.hasNext()) {
473            assertTrue(q.contains(it.next()));
474            ++i;
475        }
476        assertEquals(i, SIZE);
477    }
478
479    /**
480     * iterator of empty set has no elements
481     */
482    public void testEmptyIterator() {
483        ConcurrentSkipListSet q = new ConcurrentSkipListSet();
484        int i = 0;
485        Iterator it = q.iterator();
486        while (it.hasNext()) {
487            assertTrue(q.contains(it.next()));
488            ++i;
489        }
490        assertEquals(0, i);
491    }
492
493    /**
494     * iterator.remove removes current element
495     */
496    public void testIteratorRemove() {
497        final ConcurrentSkipListSet q = new ConcurrentSkipListSet();
498        q.add(new Integer(2));
499        q.add(new Integer(1));
500        q.add(new Integer(3));
501
502        Iterator it = q.iterator();
503        it.next();
504        it.remove();
505
506        it = q.iterator();
507        assertEquals(it.next(), new Integer(2));
508        assertEquals(it.next(), new Integer(3));
509        assertFalse(it.hasNext());
510    }
511
512    /**
513     * toString contains toStrings of elements
514     */
515    public void testToString() {
516        ConcurrentSkipListSet q = populatedSet(SIZE);
517        String s = q.toString();
518        for (int i = 0; i < SIZE; ++i) {
519            assertTrue(s.contains(String.valueOf(i)));
520        }
521    }
522
523    /**
524     * A deserialized serialized set has same elements
525     */
526    public void testSerialization() throws Exception {
527        NavigableSet x = populatedSet(SIZE);
528        NavigableSet y = serialClone(x);
529
530        assertNotSame(x, y);
531        assertEquals(x.size(), y.size());
532        assertEquals(x, y);
533        assertEquals(y, x);
534        while (!x.isEmpty()) {
535            assertFalse(y.isEmpty());
536            assertEquals(x.pollFirst(), y.pollFirst());
537        }
538        assertTrue(y.isEmpty());
539    }
540
541    /**
542     * subSet returns set with keys in requested range
543     */
544    public void testSubSetContents() {
545        ConcurrentSkipListSet set = set5();
546        SortedSet sm = set.subSet(two, four);
547        assertEquals(two, sm.first());
548        assertEquals(three, sm.last());
549        assertEquals(2, sm.size());
550        assertFalse(sm.contains(one));
551        assertTrue(sm.contains(two));
552        assertTrue(sm.contains(three));
553        assertFalse(sm.contains(four));
554        assertFalse(sm.contains(five));
555        Iterator i = sm.iterator();
556        Object k;
557        k = (Integer)(i.next());
558        assertEquals(two, k);
559        k = (Integer)(i.next());
560        assertEquals(three, k);
561        assertFalse(i.hasNext());
562        Iterator j = sm.iterator();
563        j.next();
564        j.remove();
565        assertFalse(set.contains(two));
566        assertEquals(4, set.size());
567        assertEquals(1, sm.size());
568        assertEquals(three, sm.first());
569        assertEquals(three, sm.last());
570        assertTrue(sm.remove(three));
571        assertTrue(sm.isEmpty());
572        assertEquals(3, set.size());
573    }
574
575    public void testSubSetContents2() {
576        ConcurrentSkipListSet set = set5();
577        SortedSet sm = set.subSet(two, three);
578        assertEquals(1, sm.size());
579        assertEquals(two, sm.first());
580        assertEquals(two, sm.last());
581        assertFalse(sm.contains(one));
582        assertTrue(sm.contains(two));
583        assertFalse(sm.contains(three));
584        assertFalse(sm.contains(four));
585        assertFalse(sm.contains(five));
586        Iterator i = sm.iterator();
587        Object k;
588        k = (Integer)(i.next());
589        assertEquals(two, k);
590        assertFalse(i.hasNext());
591        Iterator j = sm.iterator();
592        j.next();
593        j.remove();
594        assertFalse(set.contains(two));
595        assertEquals(4, set.size());
596        assertEquals(0, sm.size());
597        assertTrue(sm.isEmpty());
598        assertFalse(sm.remove(three));
599        assertEquals(4, set.size());
600    }
601
602    /**
603     * headSet returns set with keys in requested range
604     */
605    public void testHeadSetContents() {
606        ConcurrentSkipListSet set = set5();
607        SortedSet sm = set.headSet(four);
608        assertTrue(sm.contains(one));
609        assertTrue(sm.contains(two));
610        assertTrue(sm.contains(three));
611        assertFalse(sm.contains(four));
612        assertFalse(sm.contains(five));
613        Iterator i = sm.iterator();
614        Object k;
615        k = (Integer)(i.next());
616        assertEquals(one, k);
617        k = (Integer)(i.next());
618        assertEquals(two, k);
619        k = (Integer)(i.next());
620        assertEquals(three, k);
621        assertFalse(i.hasNext());
622        sm.clear();
623        assertTrue(sm.isEmpty());
624        assertEquals(2, set.size());
625        assertEquals(four, set.first());
626    }
627
628    /**
629     * tailSet returns set with keys in requested range
630     */
631    public void testTailSetContents() {
632        ConcurrentSkipListSet set = set5();
633        SortedSet sm = set.tailSet(two);
634        assertFalse(sm.contains(one));
635        assertTrue(sm.contains(two));
636        assertTrue(sm.contains(three));
637        assertTrue(sm.contains(four));
638        assertTrue(sm.contains(five));
639        Iterator i = sm.iterator();
640        Object k;
641        k = (Integer)(i.next());
642        assertEquals(two, k);
643        k = (Integer)(i.next());
644        assertEquals(three, k);
645        k = (Integer)(i.next());
646        assertEquals(four, k);
647        k = (Integer)(i.next());
648        assertEquals(five, k);
649        assertFalse(i.hasNext());
650
651        SortedSet ssm = sm.tailSet(four);
652        assertEquals(four, ssm.first());
653        assertEquals(five, ssm.last());
654        assertTrue(ssm.remove(four));
655        assertEquals(1, ssm.size());
656        assertEquals(3, sm.size());
657        assertEquals(4, set.size());
658    }
659
660    Random rnd = new Random(666);
661
662    /**
663     * Subsets of subsets subdivide correctly
664     */
665    public void testRecursiveSubSets() throws Exception {
666        int setSize = expensiveTests ? 1000 : 100;
667        Class cl = ConcurrentSkipListSet.class;
668
669        NavigableSet<Integer> set = newSet(cl);
670        BitSet bs = new BitSet(setSize);
671
672        populate(set, setSize, bs);
673        check(set,                 0, setSize - 1, true, bs);
674        check(set.descendingSet(), 0, setSize - 1, false, bs);
675
676        mutateSet(set, 0, setSize - 1, bs);
677        check(set,                 0, setSize - 1, true, bs);
678        check(set.descendingSet(), 0, setSize - 1, false, bs);
679
680        bashSubSet(set.subSet(0, true, setSize, false),
681                   0, setSize - 1, true, bs);
682    }
683
684    /**
685     * addAll is idempotent
686     */
687    public void testAddAll_idempotent() throws Exception {
688        Set x = populatedSet(SIZE);
689        Set y = new ConcurrentSkipListSet(x);
690        y.addAll(x);
691        assertEquals(x, y);
692        assertEquals(y, x);
693    }
694
695    static NavigableSet<Integer> newSet(Class cl) throws Exception {
696        NavigableSet<Integer> result = (NavigableSet<Integer>) cl.newInstance();
697        assertEquals(0, result.size());
698        assertFalse(result.iterator().hasNext());
699        return result;
700    }
701
702    void populate(NavigableSet<Integer> set, int limit, BitSet bs) {
703        for (int i = 0, n = 2 * limit / 3; i < n; i++) {
704            int element = rnd.nextInt(limit);
705            put(set, element, bs);
706        }
707    }
708
709    void mutateSet(NavigableSet<Integer> set, int min, int max, BitSet bs) {
710        int size = set.size();
711        int rangeSize = max - min + 1;
712
713        // Remove a bunch of entries directly
714        for (int i = 0, n = rangeSize / 2; i < n; i++) {
715            remove(set, min - 5 + rnd.nextInt(rangeSize + 10), bs);
716        }
717
718        // Remove a bunch of entries with iterator
719        for (Iterator<Integer> it = set.iterator(); it.hasNext(); ) {
720            if (rnd.nextBoolean()) {
721                bs.clear(it.next());
722                it.remove();
723            }
724        }
725
726        // Add entries till we're back to original size
727        while (set.size() < size) {
728            int element = min + rnd.nextInt(rangeSize);
729            assertTrue(element >= min && element<= max);
730            put(set, element, bs);
731        }
732    }
733
734    void mutateSubSet(NavigableSet<Integer> set, int min, int max,
735                      BitSet bs) {
736        int size = set.size();
737        int rangeSize = max - min + 1;
738
739        // Remove a bunch of entries directly
740        for (int i = 0, n = rangeSize / 2; i < n; i++) {
741            remove(set, min - 5 + rnd.nextInt(rangeSize + 10), bs);
742        }
743
744        // Remove a bunch of entries with iterator
745        for (Iterator<Integer> it = set.iterator(); it.hasNext(); ) {
746            if (rnd.nextBoolean()) {
747                bs.clear(it.next());
748                it.remove();
749            }
750        }
751
752        // Add entries till we're back to original size
753        while (set.size() < size) {
754            int element = min - 5 + rnd.nextInt(rangeSize + 10);
755            if (element >= min && element<= max) {
756                put(set, element, bs);
757            } else {
758                try {
759                    set.add(element);
760                    shouldThrow();
761                } catch (IllegalArgumentException success) {}
762            }
763        }
764    }
765
766    void put(NavigableSet<Integer> set, int element, BitSet bs) {
767        if (set.add(element))
768            bs.set(element);
769    }
770
771    void remove(NavigableSet<Integer> set, int element, BitSet bs) {
772        if (set.remove(element))
773            bs.clear(element);
774    }
775
776    void bashSubSet(NavigableSet<Integer> set,
777                    int min, int max, boolean ascending,
778                    BitSet bs) {
779        check(set, min, max, ascending, bs);
780        check(set.descendingSet(), min, max, !ascending, bs);
781
782        mutateSubSet(set, min, max, bs);
783        check(set, min, max, ascending, bs);
784        check(set.descendingSet(), min, max, !ascending, bs);
785
786        // Recurse
787        if (max - min < 2)
788            return;
789        int midPoint = (min + max) / 2;
790
791        // headSet - pick direction and endpoint inclusion randomly
792        boolean incl = rnd.nextBoolean();
793        NavigableSet<Integer> hm = set.headSet(midPoint, incl);
794        if (ascending) {
795            if (rnd.nextBoolean())
796                bashSubSet(hm, min, midPoint - (incl ? 0 : 1), true, bs);
797            else
798                bashSubSet(hm.descendingSet(), min, midPoint - (incl ? 0 : 1),
799                           false, bs);
800        } else {
801            if (rnd.nextBoolean())
802                bashSubSet(hm, midPoint + (incl ? 0 : 1), max, false, bs);
803            else
804                bashSubSet(hm.descendingSet(), midPoint + (incl ? 0 : 1), max,
805                           true, bs);
806        }
807
808        // tailSet - pick direction and endpoint inclusion randomly
809        incl = rnd.nextBoolean();
810        NavigableSet<Integer> tm = set.tailSet(midPoint,incl);
811        if (ascending) {
812            if (rnd.nextBoolean())
813                bashSubSet(tm, midPoint + (incl ? 0 : 1), max, true, bs);
814            else
815                bashSubSet(tm.descendingSet(), midPoint + (incl ? 0 : 1), max,
816                           false, bs);
817        } else {
818            if (rnd.nextBoolean()) {
819                bashSubSet(tm, min, midPoint - (incl ? 0 : 1), false, bs);
820            } else {
821                bashSubSet(tm.descendingSet(), min, midPoint - (incl ? 0 : 1),
822                           true, bs);
823            }
824        }
825
826        // subSet - pick direction and endpoint inclusion randomly
827        int rangeSize = max - min + 1;
828        int[] endpoints = new int[2];
829        endpoints[0] = min + rnd.nextInt(rangeSize);
830        endpoints[1] = min + rnd.nextInt(rangeSize);
831        Arrays.sort(endpoints);
832        boolean lowIncl = rnd.nextBoolean();
833        boolean highIncl = rnd.nextBoolean();
834        if (ascending) {
835            NavigableSet<Integer> sm = set.subSet(
836                endpoints[0], lowIncl, endpoints[1], highIncl);
837            if (rnd.nextBoolean())
838                bashSubSet(sm, endpoints[0] + (lowIncl ? 0 : 1),
839                           endpoints[1] - (highIncl ? 0 : 1), true, bs);
840            else
841                bashSubSet(sm.descendingSet(), endpoints[0] + (lowIncl ? 0 : 1),
842                           endpoints[1] - (highIncl ? 0 : 1), false, bs);
843        } else {
844            NavigableSet<Integer> sm = set.subSet(
845                endpoints[1], highIncl, endpoints[0], lowIncl);
846            if (rnd.nextBoolean())
847                bashSubSet(sm, endpoints[0] + (lowIncl ? 0 : 1),
848                           endpoints[1] - (highIncl ? 0 : 1), false, bs);
849            else
850                bashSubSet(sm.descendingSet(), endpoints[0] + (lowIncl ? 0 : 1),
851                           endpoints[1] - (highIncl ? 0 : 1), true, bs);
852        }
853    }
854
855    /**
856     * min and max are both inclusive.  If max < min, interval is empty.
857     */
858    void check(NavigableSet<Integer> set,
859               final int min, final int max, final boolean ascending,
860               final BitSet bs) {
861        class ReferenceSet {
862            int lower(int element) {
863                return ascending ?
864                    lowerAscending(element) : higherAscending(element);
865            }
866            int floor(int element) {
867                return ascending ?
868                    floorAscending(element) : ceilingAscending(element);
869            }
870            int ceiling(int element) {
871                return ascending ?
872                    ceilingAscending(element) : floorAscending(element);
873            }
874            int higher(int element) {
875                return ascending ?
876                    higherAscending(element) : lowerAscending(element);
877            }
878            int first() {
879                return ascending ? firstAscending() : lastAscending();
880            }
881            int last() {
882                return ascending ? lastAscending() : firstAscending();
883            }
884            int lowerAscending(int element) {
885                return floorAscending(element - 1);
886            }
887            int floorAscending(int element) {
888                if (element < min)
889                    return -1;
890                else if (element > max)
891                    element = max;
892
893                // BitSet should support this! Test would run much faster
894                while (element >= min) {
895                    if (bs.get(element))
896                        return element;
897                    element--;
898                }
899                return -1;
900            }
901            int ceilingAscending(int element) {
902                if (element < min)
903                    element = min;
904                else if (element > max)
905                    return -1;
906                int result = bs.nextSetBit(element);
907                return result > max ? -1 : result;
908            }
909            int higherAscending(int element) {
910                return ceilingAscending(element + 1);
911            }
912            private int firstAscending() {
913                int result = ceilingAscending(min);
914                return result > max ? -1 : result;
915            }
916            private int lastAscending() {
917                int result = floorAscending(max);
918                return result < min ? -1 : result;
919            }
920        }
921        ReferenceSet rs = new ReferenceSet();
922
923        // Test contents using containsElement
924        int size = 0;
925        for (int i = min; i <= max; i++) {
926            boolean bsContainsI = bs.get(i);
927            assertEquals(bsContainsI, set.contains(i));
928            if (bsContainsI)
929                size++;
930        }
931        assertEquals(size, set.size());
932
933        // Test contents using contains elementSet iterator
934        int size2 = 0;
935        int previousElement = -1;
936        for (int element : set) {
937            assertTrue(bs.get(element));
938            size2++;
939            assertTrue(previousElement < 0 || (ascending ?
940                element - previousElement > 0 : element - previousElement < 0));
941            previousElement = element;
942        }
943        assertEquals(size2, size);
944
945        // Test navigation ops
946        for (int element = min - 1; element <= max + 1; element++) {
947            assertEq(set.lower(element), rs.lower(element));
948            assertEq(set.floor(element), rs.floor(element));
949            assertEq(set.higher(element), rs.higher(element));
950            assertEq(set.ceiling(element), rs.ceiling(element));
951        }
952
953        // Test extrema
954        if (set.size() != 0) {
955            assertEq(set.first(), rs.first());
956            assertEq(set.last(), rs.last());
957        } else {
958            assertEq(rs.first(), -1);
959            assertEq(rs.last(),  -1);
960            try {
961                set.first();
962                shouldThrow();
963            } catch (NoSuchElementException success) {}
964            try {
965                set.last();
966                shouldThrow();
967            } catch (NoSuchElementException success) {}
968        }
969    }
970
971    static void assertEq(Integer i, int j) {
972        if (i == null)
973            assertEquals(j, -1);
974        else
975            assertEquals((int) i, j);
976    }
977
978    static boolean eq(Integer i, int j) {
979        return i == null ? j == -1 : i == j;
980    }
981
982}
983