test/tck/ConcurrentLinkedQueueTest.java

/*
 * Written by Doug Lea with assistance from members of JCP JSR-166
 * Expert Group and released to the public domain, as explained at
 * http://creativecommons.org/publicdomain/zero/1.0/
 * Other contributors include Andrew Wright, Jeffrey Hayes,
 * Pat Fisher, Mike Judd.
 */

import java.util.Arrays;
import java.util.Collection;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.Queue;
import java.util.concurrent.ConcurrentLinkedQueue;

import junit.framework.Test;

public class ConcurrentLinkedQueueTest extends JSR166TestCase {

    public static void main(String[] args) {
        main(suite(), args);
    }

    public static Test suite() {
        class Implementation implements CollectionImplementation {
            public Class<?> klazz() { return ConcurrentLinkedQueue.class; }
            public Collection emptyCollection() { return new ConcurrentLinkedQueue(); }
            public Object makeElement(int i) { return JSR166TestCase.itemFor(i); }
            public boolean isConcurrent() { return true; }
            public boolean permitsNulls() { return false; }
        }
        return newTestSuite(ConcurrentLinkedQueueTest.class,
                            CollectionTest.testSuite(new Implementation()));
    }

    /**
     * Returns a new queue of given size containing consecutive
     * Items 0 ... n - 1.
     */
    private static ConcurrentLinkedQueue<Item> populatedQueue(int n) {
        ConcurrentLinkedQueue<Item> q = new ConcurrentLinkedQueue<>();
        assertTrue(q.isEmpty());
        for (int i = 0; i < n; ++i)
            mustOffer(q, i);
        assertFalse(q.isEmpty());
        mustEqual(n, q.size());
        mustEqual(0, q.peek());
        return q;
    }

    /**
     * new queue is empty
     */
    public void testConstructor1() {
        mustEqual(0, new ConcurrentLinkedQueue<Item>().size());
    }

    /**
     * Initializing from null Collection throws NPE
     */
    public void testConstructor3() {
        try {
            new ConcurrentLinkedQueue<Item>((Collection<Item>)null);
            shouldThrow();
        } catch (NullPointerException success) {}
    }

    /**
     * Initializing from Collection of null elements throws NPE
     */
    public void testConstructor4() {
        try {
            new ConcurrentLinkedQueue<Item>(Arrays.asList(new Item[SIZE]));
            shouldThrow();
        } catch (NullPointerException success) {}
    }

    /**
     * Initializing from Collection with some null elements throws NPE
     */
    public void testConstructor5() {
        Item[] items = new Item[2];
        items[0] = zero;
        try {
            new ConcurrentLinkedQueue<Item>(Arrays.asList(items));
            shouldThrow();
        } catch (NullPointerException success) {}
    }

    /**
     * Queue contains all elements of collection used to initialize
     */
    public void testConstructor6() {
        Item[] items = defaultItems;
        ConcurrentLinkedQueue<Item> q = new ConcurrentLinkedQueue<>(Arrays.asList(items));
        for (int i = 0; i < SIZE; ++i)
            mustEqual(items[i], q.poll());
    }

    /**
     * isEmpty is true before add, false after
     */
    public void testEmpty() {
        ConcurrentLinkedQueue<Item> q = new ConcurrentLinkedQueue<>();
        assertTrue(q.isEmpty());
        q.add(one);
        assertFalse(q.isEmpty());
        q.add(two);
        q.remove();
        q.remove();
        assertTrue(q.isEmpty());
    }

    /**
     * size changes when elements added and removed
     */
    public void testSize() {
        ConcurrentLinkedQueue<Item> q = populatedQueue(SIZE);
        for (int i = 0; i < SIZE; ++i) {
            mustEqual(SIZE - i, q.size());
            q.remove();
        }
        for (int i = 0; i < SIZE; ++i) {
            mustEqual(i, q.size());
            mustAdd(q, i);
        }
    }

    /**
     * offer(null) throws NPE
     */
    public void testOfferNull() {
        ConcurrentLinkedQueue<Item> q = new ConcurrentLinkedQueue<>();
        try {
            q.offer(null);
            shouldThrow();
        } catch (NullPointerException success) {}
    }

    /**
     * add(null) throws NPE
     */
    public void testAddNull() {
        ConcurrentLinkedQueue<Item> q = new ConcurrentLinkedQueue<>();
        try {
            q.add(null);
            shouldThrow();
        } catch (NullPointerException success) {}
    }

    /**
     * Offer returns true
     */
    public void testOffer() {
        ConcurrentLinkedQueue<Item> q = new ConcurrentLinkedQueue<>();
        assertTrue(q.offer(zero));
        assertTrue(q.offer(one));
    }

    /**
     * add returns true
     */
    public void testAdd() {
        ConcurrentLinkedQueue<Item> q = new ConcurrentLinkedQueue<>();
        for (int i = 0; i < SIZE; ++i) {
            mustEqual(i, q.size());
            mustAdd(q, i);
        }
    }

    /**
     * addAll(null) throws NullPointerException
     */
    public void testAddAll1() {
        ConcurrentLinkedQueue<Item> q = new ConcurrentLinkedQueue<>();
        try {
            q.addAll(null);
            shouldThrow();
        } catch (NullPointerException success) {}
    }

    /**
     * addAll(this) throws IllegalArgumentException
     */
    public void testAddAllSelf() {
        ConcurrentLinkedQueue<Item> q = populatedQueue(SIZE);
        try {
            q.addAll(q);
            shouldThrow();
        } catch (IllegalArgumentException success) {}
    }

    /**
     * addAll of a collection with null elements throws NullPointerException
     */
    public void testAddAll2() {
        ConcurrentLinkedQueue<Item> q = new ConcurrentLinkedQueue<>();
        try {
            q.addAll(Arrays.asList(new Item[SIZE]));
            shouldThrow();
        } catch (NullPointerException success) {}
    }

    /**
     * addAll of a collection with any null elements throws NPE after
     * possibly adding some elements
     */
    public void testAddAll3() {
        ConcurrentLinkedQueue<Item> q = new ConcurrentLinkedQueue<>();
        Item[] items = new Item[2];
        items[0] = zero;
        try {
            q.addAll(Arrays.asList(items));
            shouldThrow();
        } catch (NullPointerException success) {}
    }

    /**
     * Queue contains all elements, in traversal order, of successful addAll
     */
    public void testAddAll5() {
        Item[] empty = new Item[0];
        Item[] items = defaultItems;
        ConcurrentLinkedQueue<Item> q = new ConcurrentLinkedQueue<>();
        assertFalse(q.addAll(Arrays.asList(empty)));
        assertTrue(q.addAll(Arrays.asList(items)));
        for (int i = 0; i < SIZE; ++i)
            mustEqual(items[i], q.poll());
    }

    /**
     * poll succeeds unless empty
     */
    public void testPoll() {
        ConcurrentLinkedQueue<Item> q = populatedQueue(SIZE);
        for (int i = 0; i < SIZE; ++i) {
            mustEqual(i, q.poll());
        }
        assertNull(q.poll());
    }

    /**
     * peek returns next element, or null if empty
     */
    public void testPeek() {
        ConcurrentLinkedQueue<Item> q = populatedQueue(SIZE);
        for (int i = 0; i < SIZE; ++i) {
            mustEqual(i, q.peek());
            mustEqual(i, q.poll());
            assertTrue(q.peek() == null ||
                       !q.peek().equals(i));
        }
        assertNull(q.peek());
    }

    /**
     * element returns next element, or throws NSEE if empty
     */
    public void testElement() {
        ConcurrentLinkedQueue<Item> q = populatedQueue(SIZE);
        for (int i = 0; i < SIZE; ++i) {
            mustEqual(i, q.element());
            mustEqual(i, q.poll());
        }
        try {
            q.element();
            shouldThrow();
        } catch (NoSuchElementException success) {}
    }

    /**
     * remove removes next element, or throws NSEE if empty
     */
    public void testRemove() {
        ConcurrentLinkedQueue<Item> q = populatedQueue(SIZE);
        for (int i = 0; i < SIZE; ++i) {
            mustEqual(i, q.remove());
        }
        try {
            q.remove();
            shouldThrow();
        } catch (NoSuchElementException success) {}
    }

    /**
     * remove(x) removes x and returns true if present
     */
    public void testRemoveElement() {
        ConcurrentLinkedQueue<Item> q = populatedQueue(SIZE);
        for (int i = 1; i < SIZE; i += 2) {
            mustContain(q, i);
            mustRemove(q, i);
            mustNotContain(q, i);
            mustContain(q, i - 1);
        }
        for (int i = 0; i < SIZE; i += 2) {
            mustContain(q, i);
            mustRemove(q, i);
            mustNotContain(q, i);
            mustNotRemove(q, i + 1);
            mustNotContain(q, i + 1);
        }
        assertTrue(q.isEmpty());
    }

    /**
     * contains(x) reports true when elements added but not yet removed
     */
    public void testContains() {
        ConcurrentLinkedQueue<Item> q = populatedQueue(SIZE);
        for (int i = 0; i < SIZE; ++i) {
            mustContain(q, i);
            q.poll();
            mustNotContain(q, i);
        }
    }

    /**
     * clear removes all elements
     */
    public void testClear() {
        ConcurrentLinkedQueue<Item> q = populatedQueue(SIZE);
        q.clear();
        assertTrue(q.isEmpty());
        mustEqual(0, q.size());
        q.add(one);
        assertFalse(q.isEmpty());
        q.clear();
        assertTrue(q.isEmpty());
    }

    /**
     * containsAll(c) is true when c contains a subset of elements
     */
    public void testContainsAll() {
        ConcurrentLinkedQueue<Item> q = populatedQueue(SIZE);
        ConcurrentLinkedQueue<Item> p = new ConcurrentLinkedQueue<>();
        for (int i = 0; i < SIZE; ++i) {
            assertTrue(q.containsAll(p));
            assertFalse(p.containsAll(q));
            mustAdd(p, i);
        }
        assertTrue(p.containsAll(q));
    }

    /**
     * retainAll(c) retains only those elements of c and reports true if change
     */
    public void testRetainAll() {
        ConcurrentLinkedQueue<Item> q = populatedQueue(SIZE);
        ConcurrentLinkedQueue<Item> p = populatedQueue(SIZE);
        for (int i = 0; i < SIZE; ++i) {
            boolean changed = q.retainAll(p);
            if (i == 0)
                assertFalse(changed);
            else
                assertTrue(changed);

            assertTrue(q.containsAll(p));
            mustEqual(SIZE - i, q.size());
            p.remove();
        }
    }

    /**
     * removeAll(c) removes only those elements of c and reports true if changed
     */
    public void testRemoveAll() {
        for (int i = 1; i < SIZE; ++i) {
            ConcurrentLinkedQueue<Item> q = populatedQueue(SIZE);
            ConcurrentLinkedQueue<Item> p = populatedQueue(i);
            assertTrue(q.removeAll(p));
            mustEqual(SIZE - i, q.size());
            for (int j = 0; j < i; ++j) {
                Item x = p.remove();
                assertFalse(q.contains(x));
            }
        }
    }

    /**
     * toArray contains all elements in FIFO order
     */
    public void testToArray() {
        ConcurrentLinkedQueue<Item> q = populatedQueue(SIZE);
        Object[] a = q.toArray();
        assertSame(Object[].class, a.getClass());
        for (Object o : a)
            assertSame(o, q.poll());
        assertTrue(q.isEmpty());
    }

    /**
     * toArray(a) contains all elements in FIFO order
     */
    public void testToArray2() {
        ConcurrentLinkedQueue<Item> q = populatedQueue(SIZE);
        Item[] items = new Item[SIZE];
        Item[] array = q.toArray(items);
        assertSame(items, array);
        for (Item o : items)
            assertSame(o, q.poll());
        assertTrue(q.isEmpty());
    }

    /**
     * toArray(null) throws NullPointerException
     */
    public void testToArray_NullArg() {
        ConcurrentLinkedQueue<Item> q = populatedQueue(SIZE);
        try {
            q.toArray((Object[])null);
            shouldThrow();
        } catch (NullPointerException success) {}
    }

    /**
     * toArray(incompatible array type) throws ArrayStoreException
     */
    @SuppressWarnings("CollectionToArraySafeParameter")
    public void testToArray_incompatibleArrayType() {
        ConcurrentLinkedQueue<Item> q = populatedQueue(SIZE);
        try {
            q.toArray(new String[10]);
            shouldThrow();
        } catch (ArrayStoreException success) {}
    }

    /**
     * iterator iterates through all elements
     */
    public void testIterator() {
        ConcurrentLinkedQueue<Item> q = populatedQueue(SIZE);
        Iterator<? extends Item> it = q.iterator();
        int i;
        for (i = 0; it.hasNext(); i++)
            mustContain(q, it.next());
        mustEqual(i, SIZE);
        assertIteratorExhausted(it);
    }

    /**
     * iterator of empty collection has no elements
     */
    public void testEmptyIterator() {
        assertIteratorExhausted(new ConcurrentLinkedQueue<>().iterator());
    }

    /**
     * iterator ordering is FIFO
     */
    public void testIteratorOrdering() {
        final ConcurrentLinkedQueue<Item> q = new ConcurrentLinkedQueue<>();
        q.add(one);
        q.add(two);
        q.add(three);

        int k = 0;
        for (Iterator<? extends Item> it = q.iterator(); it.hasNext();) {
            mustEqual(++k, it.next());
        }

        mustEqual(3, k);
    }

    /**
     * Modifications do not cause iterators to fail
     */
    public void testWeaklyConsistentIteration() {
        final ConcurrentLinkedQueue<Item> q = new ConcurrentLinkedQueue<>();
        q.add(one);
        q.add(two);
        q.add(three);

        for (Iterator<? extends Item> it = q.iterator(); it.hasNext();) {
            q.remove();
            it.next();
        }

        mustEqual(0, q.size());
    }

    /**
     * iterator.remove removes current element
     */
    public void testIteratorRemove() {
        final ConcurrentLinkedQueue<Item> q = new ConcurrentLinkedQueue<>();
        q.add(one);
        q.add(two);
        q.add(three);
        Iterator<? extends Item> it = q.iterator();
        it.next();
        it.remove();
        it = q.iterator();
        assertSame(it.next(), two);
        assertSame(it.next(), three);
        assertFalse(it.hasNext());
    }

    /**
     * toString contains toStrings of elements
     */
    public void testToString() {
        ConcurrentLinkedQueue<Item> q = populatedQueue(SIZE);
        String s = q.toString();
        for (int i = 0; i < SIZE; ++i) {
            assertTrue(s.contains(String.valueOf(i)));
        }
    }

    /**
     * A deserialized/reserialized queue has same elements in same order
     */
    public void testSerialization() throws Exception {
        Queue<Item> x = populatedQueue(SIZE);
        Queue<Item> y = serialClone(x);

        assertNotSame(x, y);
        mustEqual(x.size(), y.size());
        mustEqual(x.toString(), y.toString());
        assertTrue(Arrays.equals(x.toArray(), y.toArray()));
        while (!x.isEmpty()) {
            assertFalse(y.isEmpty());
            mustEqual(x.remove(), y.remove());
        }
        assertTrue(y.isEmpty());
    }

    /**
     * remove(null), contains(null) always return false
     */
    public void testNeverContainsNull() {
        Collection<?>[] qs = {
            new ConcurrentLinkedQueue<>(),
            populatedQueue(2),
        };

        for (Collection<?> q : qs) {
            assertFalse(q.contains(null));
            assertFalse(q.remove(null));
        }
    }
}
Revision:	1.52
Committed:	Wed Jan 27 02:55:18 2021 UTC (3 years, 2 months ago) by jsr166
Branch:	MAIN
CVS Tags:	HEAD
Changes since 1.51:	+2 -1 lines
Log Message:	Suppress all new errorprone "errors"
#	Content
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	* Other contributors include Andrew Wright, Jeffrey Hayes,
6	* Pat Fisher, Mike Judd.
7	*/
8
9	import java.util.Arrays;
10	import java.util.Collection;
11	import java.util.Iterator;
12	import java.util.NoSuchElementException;
13	import java.util.Queue;
14	import java.util.concurrent.ConcurrentLinkedQueue;
15
16	import junit.framework.Test;
17
18	public class ConcurrentLinkedQueueTest extends JSR166TestCase {
19
20	public static void main(String[] args) {
21	main(suite(), args);
22	}
23
24	public static Test suite() {
25	class Implementation implements CollectionImplementation {
26	public Class<?> klazz() { return ConcurrentLinkedQueue.class; }
27	public Collection emptyCollection() { return new ConcurrentLinkedQueue(); }
28	public Object makeElement(int i) { return JSR166TestCase.itemFor(i); }
29	public boolean isConcurrent() { return true; }
30	public boolean permitsNulls() { return false; }
31	}
32	return newTestSuite(ConcurrentLinkedQueueTest.class,
33	CollectionTest.testSuite(new Implementation()));
34	}
35
36	/**
37	* Returns a new queue of given size containing consecutive
38	* Items 0 ... n - 1.
39	*/
40	private static ConcurrentLinkedQueue<Item> populatedQueue(int n) {
41	ConcurrentLinkedQueue<Item> q = new ConcurrentLinkedQueue<>();
42	assertTrue(q.isEmpty());
43	for (int i = 0; i < n; ++i)
44	mustOffer(q, i);
45	assertFalse(q.isEmpty());
46	mustEqual(n, q.size());
47	mustEqual(0, q.peek());
48	return q;
49	}
50
51	/**
52	* new queue is empty
53	*/
54	public void testConstructor1() {
55	mustEqual(0, new ConcurrentLinkedQueue<Item>().size());
56	}
57
58	/**
59	* Initializing from null Collection throws NPE
60	*/
61	public void testConstructor3() {
62	try {
63	new ConcurrentLinkedQueue<Item>((Collection<Item>)null);
64	shouldThrow();
65	} catch (NullPointerException success) {}
66	}
67
68	/**
69	* Initializing from Collection of null elements throws NPE
70	*/
71	public void testConstructor4() {
72	try {
73	new ConcurrentLinkedQueue<Item>(Arrays.asList(new Item[SIZE]));
74	shouldThrow();
75	} catch (NullPointerException success) {}
76	}
77
78	/**
79	* Initializing from Collection with some null elements throws NPE
80	*/
81	public void testConstructor5() {
82	Item[] items = new Item[2];
83	items[0] = zero;
84	try {
85	new ConcurrentLinkedQueue<Item>(Arrays.asList(items));
86	shouldThrow();
87	} catch (NullPointerException success) {}
88	}
89
90	/**
91	* Queue contains all elements of collection used to initialize
92	*/
93	public void testConstructor6() {
94	Item[] items = defaultItems;
95	ConcurrentLinkedQueue<Item> q = new ConcurrentLinkedQueue<>(Arrays.asList(items));
96	for (int i = 0; i < SIZE; ++i)
97	mustEqual(items[i], q.poll());
98	}
99
100	/**
101	* isEmpty is true before add, false after
102	*/
103	public void testEmpty() {
104	ConcurrentLinkedQueue<Item> q = new ConcurrentLinkedQueue<>();
105	assertTrue(q.isEmpty());
106	q.add(one);
107	assertFalse(q.isEmpty());
108	q.add(two);
109	q.remove();
110	q.remove();
111	assertTrue(q.isEmpty());
112	}
113
114	/**
115	* size changes when elements added and removed
116	*/
117	public void testSize() {
118	ConcurrentLinkedQueue<Item> q = populatedQueue(SIZE);
119	for (int i = 0; i < SIZE; ++i) {
120	mustEqual(SIZE - i, q.size());
121	q.remove();
122	}
123	for (int i = 0; i < SIZE; ++i) {
124	mustEqual(i, q.size());
125	mustAdd(q, i);
126	}
127	}
128
129	/**
130	* offer(null) throws NPE
131	*/
132	public void testOfferNull() {
133	ConcurrentLinkedQueue<Item> q = new ConcurrentLinkedQueue<>();
134	try {
135	q.offer(null);
136	shouldThrow();
137	} catch (NullPointerException success) {}
138	}
139
140	/**
141	* add(null) throws NPE
142	*/
143	public void testAddNull() {
144	ConcurrentLinkedQueue<Item> q = new ConcurrentLinkedQueue<>();
145	try {
146	q.add(null);
147	shouldThrow();
148	} catch (NullPointerException success) {}
149	}
150
151	/**
152	* Offer returns true
153	*/
154	public void testOffer() {
155	ConcurrentLinkedQueue<Item> q = new ConcurrentLinkedQueue<>();
156	assertTrue(q.offer(zero));
157	assertTrue(q.offer(one));
158	}
159
160	/**
161	* add returns true
162	*/
163	public void testAdd() {
164	ConcurrentLinkedQueue<Item> q = new ConcurrentLinkedQueue<>();
165	for (int i = 0; i < SIZE; ++i) {
166	mustEqual(i, q.size());
167	mustAdd(q, i);
168	}
169	}
170
171	/**
172	* addAll(null) throws NullPointerException
173	*/
174	public void testAddAll1() {
175	ConcurrentLinkedQueue<Item> q = new ConcurrentLinkedQueue<>();
176	try {
177	q.addAll(null);
178	shouldThrow();
179	} catch (NullPointerException success) {}
180	}
181
182	/**
183	* addAll(this) throws IllegalArgumentException
184	*/
185	public void testAddAllSelf() {
186	ConcurrentLinkedQueue<Item> q = populatedQueue(SIZE);
187	try {
188	q.addAll(q);
189	shouldThrow();
190	} catch (IllegalArgumentException success) {}
191	}
192
193	/**
194	* addAll of a collection with null elements throws NullPointerException
195	*/
196	public void testAddAll2() {
197	ConcurrentLinkedQueue<Item> q = new ConcurrentLinkedQueue<>();
198	try {
199	q.addAll(Arrays.asList(new Item[SIZE]));
200	shouldThrow();
201	} catch (NullPointerException success) {}
202	}
203
204	/**
205	* addAll of a collection with any null elements throws NPE after
206	* possibly adding some elements
207	*/
208	public void testAddAll3() {
209	ConcurrentLinkedQueue<Item> q = new ConcurrentLinkedQueue<>();
210	Item[] items = new Item[2];
211	items[0] = zero;
212	try {
213	q.addAll(Arrays.asList(items));
214	shouldThrow();
215	} catch (NullPointerException success) {}
216	}
217
218	/**
219	* Queue contains all elements, in traversal order, of successful addAll
220	*/
221	public void testAddAll5() {
222	Item[] empty = new Item[0];
223	Item[] items = defaultItems;
224	ConcurrentLinkedQueue<Item> q = new ConcurrentLinkedQueue<>();
225	assertFalse(q.addAll(Arrays.asList(empty)));
226	assertTrue(q.addAll(Arrays.asList(items)));
227	for (int i = 0; i < SIZE; ++i)
228	mustEqual(items[i], q.poll());
229	}
230
231	/**
232	* poll succeeds unless empty
233	*/
234	public void testPoll() {
235	ConcurrentLinkedQueue<Item> q = populatedQueue(SIZE);
236	for (int i = 0; i < SIZE; ++i) {
237	mustEqual(i, q.poll());
238	}
239	assertNull(q.poll());
240	}
241
242	/**
243	* peek returns next element, or null if empty
244	*/
245	public void testPeek() {
246	ConcurrentLinkedQueue<Item> q = populatedQueue(SIZE);
247	for (int i = 0; i < SIZE; ++i) {
248	mustEqual(i, q.peek());
249	mustEqual(i, q.poll());
250	assertTrue(q.peek() == null \|\|
251	!q.peek().equals(i));
252	}
253	assertNull(q.peek());
254	}
255
256	/**
257	* element returns next element, or throws NSEE if empty
258	*/
259	public void testElement() {
260	ConcurrentLinkedQueue<Item> q = populatedQueue(SIZE);
261	for (int i = 0; i < SIZE; ++i) {
262	mustEqual(i, q.element());
263	mustEqual(i, q.poll());
264	}
265	try {
266	q.element();
267	shouldThrow();
268	} catch (NoSuchElementException success) {}
269	}
270
271	/**
272	* remove removes next element, or throws NSEE if empty
273	*/
274	public void testRemove() {
275	ConcurrentLinkedQueue<Item> q = populatedQueue(SIZE);
276	for (int i = 0; i < SIZE; ++i) {
277	mustEqual(i, q.remove());
278	}
279	try {
280	q.remove();
281	shouldThrow();
282	} catch (NoSuchElementException success) {}
283	}
284
285	/**
286	* remove(x) removes x and returns true if present
287	*/
288	public void testRemoveElement() {
289	ConcurrentLinkedQueue<Item> q = populatedQueue(SIZE);
290	for (int i = 1; i < SIZE; i += 2) {
291	mustContain(q, i);
292	mustRemove(q, i);
293	mustNotContain(q, i);
294	mustContain(q, i - 1);
295	}
296	for (int i = 0; i < SIZE; i += 2) {
297	mustContain(q, i);
298	mustRemove(q, i);
299	mustNotContain(q, i);
300	mustNotRemove(q, i + 1);
301	mustNotContain(q, i + 1);
302	}
303	assertTrue(q.isEmpty());
304	}
305
306	/**
307	* contains(x) reports true when elements added but not yet removed
308	*/
309	public void testContains() {
310	ConcurrentLinkedQueue<Item> q = populatedQueue(SIZE);
311	for (int i = 0; i < SIZE; ++i) {
312	mustContain(q, i);
313	q.poll();
314	mustNotContain(q, i);
315	}
316	}
317
318	/**
319	* clear removes all elements
320	*/
321	public void testClear() {
322	ConcurrentLinkedQueue<Item> q = populatedQueue(SIZE);
323	q.clear();
324	assertTrue(q.isEmpty());
325	mustEqual(0, q.size());
326	q.add(one);
327	assertFalse(q.isEmpty());
328	q.clear();
329	assertTrue(q.isEmpty());
330	}
331
332	/**
333	* containsAll(c) is true when c contains a subset of elements
334	*/
335	public void testContainsAll() {
336	ConcurrentLinkedQueue<Item> q = populatedQueue(SIZE);
337	ConcurrentLinkedQueue<Item> p = new ConcurrentLinkedQueue<>();
338	for (int i = 0; i < SIZE; ++i) {
339	assertTrue(q.containsAll(p));
340	assertFalse(p.containsAll(q));
341	mustAdd(p, i);
342	}
343	assertTrue(p.containsAll(q));
344	}
345
346	/**
347	* retainAll(c) retains only those elements of c and reports true if change
348	*/
349	public void testRetainAll() {
350	ConcurrentLinkedQueue<Item> q = populatedQueue(SIZE);
351	ConcurrentLinkedQueue<Item> p = populatedQueue(SIZE);
352	for (int i = 0; i < SIZE; ++i) {
353	boolean changed = q.retainAll(p);
354	if (i == 0)
355	assertFalse(changed);
356	else
357	assertTrue(changed);
358
359	assertTrue(q.containsAll(p));
360	mustEqual(SIZE - i, q.size());
361	p.remove();
362	}
363	}
364
365	/**
366	* removeAll(c) removes only those elements of c and reports true if changed
367	*/
368	public void testRemoveAll() {
369	for (int i = 1; i < SIZE; ++i) {
370	ConcurrentLinkedQueue<Item> q = populatedQueue(SIZE);
371	ConcurrentLinkedQueue<Item> p = populatedQueue(i);
372	assertTrue(q.removeAll(p));
373	mustEqual(SIZE - i, q.size());
374	for (int j = 0; j < i; ++j) {
375	Item x = p.remove();
376	assertFalse(q.contains(x));
377	}
378	}
379	}
380
381	/**
382	* toArray contains all elements in FIFO order
383	*/
384	public void testToArray() {
385	ConcurrentLinkedQueue<Item> q = populatedQueue(SIZE);
386	Object[] a = q.toArray();
387	assertSame(Object[].class, a.getClass());
388	for (Object o : a)
389	assertSame(o, q.poll());
390	assertTrue(q.isEmpty());
391	}
392
393	/**
394	* toArray(a) contains all elements in FIFO order
395	*/
396	public void testToArray2() {
397	ConcurrentLinkedQueue<Item> q = populatedQueue(SIZE);
398	Item[] items = new Item[SIZE];
399	Item[] array = q.toArray(items);
400	assertSame(items, array);
401	for (Item o : items)
402	assertSame(o, q.poll());
403	assertTrue(q.isEmpty());
404	}
405
406	/**
407	* toArray(null) throws NullPointerException
408	*/
409	public void testToArray_NullArg() {
410	ConcurrentLinkedQueue<Item> q = populatedQueue(SIZE);
411	try {
412	q.toArray((Object[])null);
413	shouldThrow();
414	} catch (NullPointerException success) {}
415	}
416
417	/**
418	* toArray(incompatible array type) throws ArrayStoreException
419	*/
420	@SuppressWarnings("CollectionToArraySafeParameter")
421	public void testToArray_incompatibleArrayType() {
422	ConcurrentLinkedQueue<Item> q = populatedQueue(SIZE);
423	try {
424	q.toArray(new String[10]);
425	shouldThrow();
426	} catch (ArrayStoreException success) {}
427	}
428
429	/**
430	* iterator iterates through all elements
431	*/
432	public void testIterator() {
433	ConcurrentLinkedQueue<Item> q = populatedQueue(SIZE);
434	Iterator<? extends Item> it = q.iterator();
435	int i;
436	for (i = 0; it.hasNext(); i++)
437	mustContain(q, it.next());
438	mustEqual(i, SIZE);
439	assertIteratorExhausted(it);
440	}
441
442	/**
443	* iterator of empty collection has no elements
444	*/
445	public void testEmptyIterator() {
446	assertIteratorExhausted(new ConcurrentLinkedQueue<>().iterator());
447	}
448
449	/**
450	* iterator ordering is FIFO
451	*/
452	public void testIteratorOrdering() {
453	final ConcurrentLinkedQueue<Item> q = new ConcurrentLinkedQueue<>();
454	q.add(one);
455	q.add(two);
456	q.add(three);
457
458	int k = 0;
459	for (Iterator<? extends Item> it = q.iterator(); it.hasNext();) {
460	mustEqual(++k, it.next());
461	}
462
463	mustEqual(3, k);
464	}
465
466	/**
467	* Modifications do not cause iterators to fail
468	*/
469	public void testWeaklyConsistentIteration() {
470	final ConcurrentLinkedQueue<Item> q = new ConcurrentLinkedQueue<>();
471	q.add(one);
472	q.add(two);
473	q.add(three);
474
475	for (Iterator<? extends Item> it = q.iterator(); it.hasNext();) {
476	q.remove();
477	it.next();
478	}
479
480	mustEqual(0, q.size());
481	}
482
483	/**
484	* iterator.remove removes current element
485	*/
486	public void testIteratorRemove() {
487	final ConcurrentLinkedQueue<Item> q = new ConcurrentLinkedQueue<>();
488	q.add(one);
489	q.add(two);
490	q.add(three);
491	Iterator<? extends Item> it = q.iterator();
492	it.next();
493	it.remove();
494	it = q.iterator();
495	assertSame(it.next(), two);
496	assertSame(it.next(), three);
497	assertFalse(it.hasNext());
498	}
499
500	/**
501	* toString contains toStrings of elements
502	*/
503	public void testToString() {
504	ConcurrentLinkedQueue<Item> q = populatedQueue(SIZE);
505	String s = q.toString();
506	for (int i = 0; i < SIZE; ++i) {
507	assertTrue(s.contains(String.valueOf(i)));
508	}
509	}
510
511	/**
512	* A deserialized/reserialized queue has same elements in same order
513	*/
514	public void testSerialization() throws Exception {
515	Queue<Item> x = populatedQueue(SIZE);
516	Queue<Item> y = serialClone(x);
517
518	assertNotSame(x, y);
519	mustEqual(x.size(), y.size());
520	mustEqual(x.toString(), y.toString());
521	assertTrue(Arrays.equals(x.toArray(), y.toArray()));
522	while (!x.isEmpty()) {
523	assertFalse(y.isEmpty());
524	mustEqual(x.remove(), y.remove());
525	}
526	assertTrue(y.isEmpty());
527	}
528
529	/**
530	* remove(null), contains(null) always return false
531	*/
532	public void testNeverContainsNull() {
533	Collection<?>[] qs = {
534	new ConcurrentLinkedQueue<>(),
535	populatedQueue(2),
536	};
537
538	for (Collection<?> q : qs) {
539	assertFalse(q.contains(null));
540	assertFalse(q.remove(null));
541	}
542	}
543	}