/* * 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/ */ package jsr166; import static java.util.concurrent.TimeUnit.MILLISECONDS; import java.util.ArrayList; import java.util.Arrays; import java.util.Collection; import java.util.Deque; import java.util.Iterator; import java.util.NoSuchElementException; import java.util.Queue; import java.util.concurrent.BlockingDeque; import java.util.concurrent.BlockingQueue; import java.util.concurrent.CountDownLatch; import java.util.concurrent.Executors; import java.util.concurrent.ExecutorService; import java.util.concurrent.LinkedBlockingDeque; import junit.framework.Test; public class LinkedBlockingDequeTest extends JSR166TestCase { public static class Unbounded extends BlockingQueueTest { protected BlockingQueue emptyCollection() { return new LinkedBlockingDeque(); } } public static class Bounded extends BlockingQueueTest { protected BlockingQueue emptyCollection() { return new LinkedBlockingDeque(SIZE); } } // android-note: Removed because the CTS runner does a bad job of // retrying tests that have suite() declarations. // // public static void main(String[] args) { // main(suite(), args); // } // public static Test suite() { // return newTestSuite(LinkedBlockingDequeTest.class, // new Unbounded().testSuite(), // new Bounded().testSuite()); // } /** * Returns a new deque of given size containing consecutive * Integers 0 ... n. */ private LinkedBlockingDeque<Integer> populatedDeque(int n) { LinkedBlockingDeque<Integer> q = new LinkedBlockingDeque<Integer>(n); assertTrue(q.isEmpty()); for (int i = 0; i < n; i++) assertTrue(q.offer(new Integer(i))); assertFalse(q.isEmpty()); assertEquals(0, q.remainingCapacity()); assertEquals(n, q.size()); return q; } /** * isEmpty is true before add, false after */ public void testEmpty() { LinkedBlockingDeque q = new LinkedBlockingDeque(); assertTrue(q.isEmpty()); q.add(new Integer(1)); assertFalse(q.isEmpty()); q.add(new Integer(2)); q.removeFirst(); q.removeFirst(); assertTrue(q.isEmpty()); } /** * size changes when elements added and removed */ public void testSize() { LinkedBlockingDeque q = populatedDeque(SIZE); for (int i = 0; i < SIZE; ++i) { assertEquals(SIZE - i, q.size()); q.removeFirst(); } for (int i = 0; i < SIZE; ++i) { assertEquals(i, q.size()); q.add(new Integer(i)); } } /** * offerFirst(null) throws NullPointerException */ public void testOfferFirstNull() { LinkedBlockingDeque q = new LinkedBlockingDeque(); try { q.offerFirst(null); shouldThrow(); } catch (NullPointerException success) {} } /** * offerLast(null) throws NullPointerException */ public void testOfferLastNull() { LinkedBlockingDeque q = new LinkedBlockingDeque(); try { q.offerLast(null); shouldThrow(); } catch (NullPointerException success) {} } /** * OfferFirst succeeds */ public void testOfferFirst() { LinkedBlockingDeque q = new LinkedBlockingDeque(); assertTrue(q.offerFirst(new Integer(0))); assertTrue(q.offerFirst(new Integer(1))); } /** * OfferLast succeeds */ public void testOfferLast() { LinkedBlockingDeque q = new LinkedBlockingDeque(); assertTrue(q.offerLast(new Integer(0))); assertTrue(q.offerLast(new Integer(1))); } /** * pollFirst succeeds unless empty */ public void testPollFirst() { LinkedBlockingDeque q = populatedDeque(SIZE); for (int i = 0; i < SIZE; ++i) { assertEquals(i, q.pollFirst()); } assertNull(q.pollFirst()); } /** * pollLast succeeds unless empty */ public void testPollLast() { LinkedBlockingDeque q = populatedDeque(SIZE); for (int i = SIZE - 1; i >= 0; --i) { assertEquals(i, q.pollLast()); } assertNull(q.pollLast()); } /** * peekFirst returns next element, or null if empty */ public void testPeekFirst() { LinkedBlockingDeque q = populatedDeque(SIZE); for (int i = 0; i < SIZE; ++i) { assertEquals(i, q.peekFirst()); assertEquals(i, q.pollFirst()); assertTrue(q.peekFirst() == null || !q.peekFirst().equals(i)); } assertNull(q.peekFirst()); } /** * peek returns next element, or null if empty */ public void testPeek() { LinkedBlockingDeque q = populatedDeque(SIZE); for (int i = 0; i < SIZE; ++i) { assertEquals(i, q.peek()); assertEquals(i, q.pollFirst()); assertTrue(q.peek() == null || !q.peek().equals(i)); } assertNull(q.peek()); } /** * peekLast returns next element, or null if empty */ public void testPeekLast() { LinkedBlockingDeque q = populatedDeque(SIZE); for (int i = SIZE - 1; i >= 0; --i) { assertEquals(i, q.peekLast()); assertEquals(i, q.pollLast()); assertTrue(q.peekLast() == null || !q.peekLast().equals(i)); } assertNull(q.peekLast()); } /** * getFirst() returns first element, or throws NSEE if empty */ public void testFirstElement() { LinkedBlockingDeque q = populatedDeque(SIZE); for (int i = 0; i < SIZE; ++i) { assertEquals(i, q.getFirst()); assertEquals(i, q.pollFirst()); } try { q.getFirst(); shouldThrow(); } catch (NoSuchElementException success) {} assertNull(q.peekFirst()); } /** * getLast() returns last element, or throws NSEE if empty */ public void testLastElement() { LinkedBlockingDeque q = populatedDeque(SIZE); for (int i = SIZE - 1; i >= 0; --i) { assertEquals(i, q.getLast()); assertEquals(i, q.pollLast()); } try { q.getLast(); shouldThrow(); } catch (NoSuchElementException success) {} assertNull(q.peekLast()); } /** * removeFirst() removes first element, or throws NSEE if empty */ public void testRemoveFirst() { LinkedBlockingDeque q = populatedDeque(SIZE); for (int i = 0; i < SIZE; ++i) { assertEquals(i, q.removeFirst()); } try { q.removeFirst(); shouldThrow(); } catch (NoSuchElementException success) {} assertNull(q.peekFirst()); } /** * removeLast() removes last element, or throws NSEE if empty */ public void testRemoveLast() { LinkedBlockingDeque q = populatedDeque(SIZE); for (int i = SIZE - 1; i >= 0; --i) { assertEquals(i, q.removeLast()); } try { q.removeLast(); shouldThrow(); } catch (NoSuchElementException success) {} assertNull(q.peekLast()); } /** * remove removes next element, or throws NSEE if empty */ public void testRemove() { LinkedBlockingDeque q = populatedDeque(SIZE); for (int i = 0; i < SIZE; ++i) { assertEquals(i, q.remove()); } try { q.remove(); shouldThrow(); } catch (NoSuchElementException success) {} } /** * removeFirstOccurrence(x) removes x and returns true if present */ public void testRemoveFirstOccurrence() { LinkedBlockingDeque q = populatedDeque(SIZE); for (int i = 1; i < SIZE; i += 2) { assertTrue(q.removeFirstOccurrence(new Integer(i))); } for (int i = 0; i < SIZE; i += 2) { assertTrue(q.removeFirstOccurrence(new Integer(i))); assertFalse(q.removeFirstOccurrence(new Integer(i + 1))); } assertTrue(q.isEmpty()); } /** * removeLastOccurrence(x) removes x and returns true if present */ public void testRemoveLastOccurrence() { LinkedBlockingDeque q = populatedDeque(SIZE); for (int i = 1; i < SIZE; i += 2) { assertTrue(q.removeLastOccurrence(new Integer(i))); } for (int i = 0; i < SIZE; i += 2) { assertTrue(q.removeLastOccurrence(new Integer(i))); assertFalse(q.removeLastOccurrence(new Integer(i + 1))); } assertTrue(q.isEmpty()); } /** * peekFirst returns element inserted with addFirst */ public void testAddFirst() { LinkedBlockingDeque q = populatedDeque(3); q.pollLast(); q.addFirst(four); assertSame(four, q.peekFirst()); } /** * peekLast returns element inserted with addLast */ public void testAddLast() { LinkedBlockingDeque q = populatedDeque(3); q.pollLast(); q.addLast(four); assertSame(four, q.peekLast()); } /** * A new deque has the indicated capacity, or Integer.MAX_VALUE if * none given */ public void testConstructor1() { assertEquals(SIZE, new LinkedBlockingDeque(SIZE).remainingCapacity()); assertEquals(Integer.MAX_VALUE, new LinkedBlockingDeque().remainingCapacity()); } /** * Constructor throws IllegalArgumentException if capacity argument nonpositive */ public void testConstructor2() { try { new LinkedBlockingDeque(0); shouldThrow(); } catch (IllegalArgumentException success) {} } /** * Initializing from null Collection throws NullPointerException */ public void testConstructor3() { try { new LinkedBlockingDeque(null); shouldThrow(); } catch (NullPointerException success) {} } /** * Initializing from Collection of null elements throws NullPointerException */ public void testConstructor4() { Collection<Integer> elements = Arrays.asList(new Integer[SIZE]); try { new LinkedBlockingDeque(elements); shouldThrow(); } catch (NullPointerException success) {} } /** * Initializing from Collection with some null elements throws * NullPointerException */ public void testConstructor5() { Integer[] ints = new Integer[SIZE]; for (int i = 0; i < SIZE - 1; ++i) ints[i] = i; Collection<Integer> elements = Arrays.asList(ints); try { new LinkedBlockingDeque(elements); shouldThrow(); } catch (NullPointerException success) {} } /** * Deque contains all elements of collection used to initialize */ public void testConstructor6() { Integer[] ints = new Integer[SIZE]; for (int i = 0; i < SIZE; ++i) ints[i] = i; LinkedBlockingDeque q = new LinkedBlockingDeque(Arrays.asList(ints)); for (int i = 0; i < SIZE; ++i) assertEquals(ints[i], q.poll()); } /** * Deque transitions from empty to full when elements added */ public void testEmptyFull() { LinkedBlockingDeque q = new LinkedBlockingDeque(2); assertTrue(q.isEmpty()); assertEquals("should have room for 2", 2, q.remainingCapacity()); q.add(one); assertFalse(q.isEmpty()); q.add(two); assertFalse(q.isEmpty()); assertEquals(0, q.remainingCapacity()); assertFalse(q.offer(three)); } /** * remainingCapacity decreases on add, increases on remove */ public void testRemainingCapacity() { BlockingQueue q = populatedDeque(SIZE); for (int i = 0; i < SIZE; ++i) { assertEquals(i, q.remainingCapacity()); assertEquals(SIZE, q.size() + q.remainingCapacity()); assertEquals(i, q.remove()); } for (int i = 0; i < SIZE; ++i) { assertEquals(SIZE - i, q.remainingCapacity()); assertEquals(SIZE, q.size() + q.remainingCapacity()); assertTrue(q.add(i)); } } /** * push(null) throws NPE */ public void testPushNull() { LinkedBlockingDeque q = new LinkedBlockingDeque(1); try { q.push(null); shouldThrow(); } catch (NullPointerException success) {} } /** * push succeeds if not full; throws ISE if full */ public void testPush() { LinkedBlockingDeque q = new LinkedBlockingDeque(SIZE); for (int i = 0; i < SIZE; ++i) { Integer x = new Integer(i); q.push(x); assertEquals(x, q.peek()); } assertEquals(0, q.remainingCapacity()); try { q.push(new Integer(SIZE)); shouldThrow(); } catch (IllegalStateException success) {} } /** * peekFirst returns element inserted with push */ public void testPushWithPeek() { LinkedBlockingDeque q = populatedDeque(3); q.pollLast(); q.push(four); assertSame(four, q.peekFirst()); } /** * pop removes next element, or throws NSEE if empty */ public void testPop() { LinkedBlockingDeque q = populatedDeque(SIZE); for (int i = 0; i < SIZE; ++i) { assertEquals(i, q.pop()); } try { q.pop(); shouldThrow(); } catch (NoSuchElementException success) {} } /** * Offer succeeds if not full; fails if full */ public void testOffer() { LinkedBlockingDeque q = new LinkedBlockingDeque(1); assertTrue(q.offer(zero)); assertFalse(q.offer(one)); } /** * add succeeds if not full; throws ISE if full */ public void testAdd() { LinkedBlockingDeque q = new LinkedBlockingDeque(SIZE); for (int i = 0; i < SIZE; ++i) assertTrue(q.add(new Integer(i))); assertEquals(0, q.remainingCapacity()); try { q.add(new Integer(SIZE)); shouldThrow(); } catch (IllegalStateException success) {} } /** * addAll(this) throws IAE */ public void testAddAllSelf() { LinkedBlockingDeque q = populatedDeque(SIZE); try { q.addAll(q); shouldThrow(); } catch (IllegalArgumentException success) {} } /** * addAll of a collection with any null elements throws NPE after * possibly adding some elements */ public void testAddAll3() { LinkedBlockingDeque q = new LinkedBlockingDeque(SIZE); Integer[] ints = new Integer[SIZE]; for (int i = 0; i < SIZE - 1; ++i) ints[i] = new Integer(i); Collection<Integer> elements = Arrays.asList(ints); try { q.addAll(elements); shouldThrow(); } catch (NullPointerException success) {} } /** * addAll throws IllegalStateException if not enough room */ public void testAddAll4() { LinkedBlockingDeque q = new LinkedBlockingDeque(SIZE - 1); Integer[] ints = new Integer[SIZE]; for (int i = 0; i < SIZE; ++i) ints[i] = new Integer(i); Collection<Integer> elements = Arrays.asList(ints); try { q.addAll(elements); shouldThrow(); } catch (IllegalStateException success) {} } /** * Deque contains all elements, in traversal order, of successful addAll */ public void testAddAll5() { Integer[] empty = new Integer[0]; Integer[] ints = new Integer[SIZE]; for (int i = 0; i < SIZE; ++i) ints[i] = new Integer(i); LinkedBlockingDeque q = new LinkedBlockingDeque(SIZE); assertFalse(q.addAll(Arrays.asList(empty))); assertTrue(q.addAll(Arrays.asList(ints))); for (int i = 0; i < SIZE; ++i) assertEquals(ints[i], q.poll()); } /** * all elements successfully put are contained */ public void testPut() throws InterruptedException { LinkedBlockingDeque q = new LinkedBlockingDeque(SIZE); for (int i = 0; i < SIZE; ++i) { Integer x = new Integer(i); q.put(x); assertTrue(q.contains(x)); } assertEquals(0, q.remainingCapacity()); } /** * put blocks interruptibly if full */ public void testBlockingPut() throws InterruptedException { final LinkedBlockingDeque q = new LinkedBlockingDeque(SIZE); final CountDownLatch pleaseInterrupt = new CountDownLatch(1); Thread t = newStartedThread(new CheckedRunnable() { public void realRun() throws InterruptedException { for (int i = 0; i < SIZE; ++i) q.put(i); assertEquals(SIZE, q.size()); assertEquals(0, q.remainingCapacity()); Thread.currentThread().interrupt(); try { q.put(99); shouldThrow(); } catch (InterruptedException success) {} assertFalse(Thread.interrupted()); pleaseInterrupt.countDown(); try { q.put(99); shouldThrow(); } catch (InterruptedException success) {} assertFalse(Thread.interrupted()); }}); await(pleaseInterrupt); assertThreadStaysAlive(t); t.interrupt(); awaitTermination(t); assertEquals(SIZE, q.size()); assertEquals(0, q.remainingCapacity()); } /** * put blocks interruptibly waiting for take when full */ public void testPutWithTake() throws InterruptedException { final int capacity = 2; final LinkedBlockingDeque q = new LinkedBlockingDeque(capacity); final CountDownLatch pleaseTake = new CountDownLatch(1); final CountDownLatch pleaseInterrupt = new CountDownLatch(1); Thread t = newStartedThread(new CheckedRunnable() { public void realRun() throws InterruptedException { for (int i = 0; i < capacity; i++) q.put(i); pleaseTake.countDown(); q.put(86); pleaseInterrupt.countDown(); try { q.put(99); shouldThrow(); } catch (InterruptedException success) {} assertFalse(Thread.interrupted()); }}); await(pleaseTake); assertEquals(0, q.remainingCapacity()); assertEquals(0, q.take()); await(pleaseInterrupt); assertThreadStaysAlive(t); t.interrupt(); awaitTermination(t); assertEquals(0, q.remainingCapacity()); } /** * timed offer times out if full and elements not taken */ public void testTimedOffer() throws InterruptedException { final LinkedBlockingDeque q = new LinkedBlockingDeque(2); final CountDownLatch pleaseInterrupt = new CountDownLatch(1); Thread t = newStartedThread(new CheckedRunnable() { public void realRun() throws InterruptedException { q.put(new Object()); q.put(new Object()); long startTime = System.nanoTime(); assertFalse(q.offer(new Object(), timeoutMillis(), MILLISECONDS)); assertTrue(millisElapsedSince(startTime) >= timeoutMillis()); pleaseInterrupt.countDown(); try { q.offer(new Object(), 2 * LONG_DELAY_MS, MILLISECONDS); shouldThrow(); } catch (InterruptedException success) {} }}); await(pleaseInterrupt); assertThreadStaysAlive(t); t.interrupt(); awaitTermination(t); } /** * take retrieves elements in FIFO order */ public void testTake() throws InterruptedException { LinkedBlockingDeque q = populatedDeque(SIZE); for (int i = 0; i < SIZE; ++i) { assertEquals(i, q.take()); } } /** * take removes existing elements until empty, then blocks interruptibly */ public void testBlockingTake() throws InterruptedException { final LinkedBlockingDeque q = populatedDeque(SIZE); final CountDownLatch pleaseInterrupt = new CountDownLatch(1); Thread t = newStartedThread(new CheckedRunnable() { public void realRun() throws InterruptedException { for (int i = 0; i < SIZE; ++i) { assertEquals(i, q.take()); } Thread.currentThread().interrupt(); try { q.take(); shouldThrow(); } catch (InterruptedException success) {} assertFalse(Thread.interrupted()); pleaseInterrupt.countDown(); try { q.take(); shouldThrow(); } catch (InterruptedException success) {} assertFalse(Thread.interrupted()); }}); await(pleaseInterrupt); assertThreadStaysAlive(t); t.interrupt(); awaitTermination(t); } /** * poll succeeds unless empty */ public void testPoll() { LinkedBlockingDeque q = populatedDeque(SIZE); for (int i = 0; i < SIZE; ++i) { assertEquals(i, q.poll()); } assertNull(q.poll()); } /** * timed poll with zero timeout succeeds when non-empty, else times out */ public void testTimedPoll0() throws InterruptedException { LinkedBlockingDeque q = populatedDeque(SIZE); for (int i = 0; i < SIZE; ++i) { assertEquals(i, q.poll(0, MILLISECONDS)); } assertNull(q.poll(0, MILLISECONDS)); } /** * timed poll with nonzero timeout succeeds when non-empty, else times out */ public void testTimedPoll() throws InterruptedException { LinkedBlockingDeque q = populatedDeque(SIZE); for (int i = 0; i < SIZE; ++i) { long startTime = System.nanoTime(); assertEquals(i, q.poll(LONG_DELAY_MS, MILLISECONDS)); assertTrue(millisElapsedSince(startTime) < LONG_DELAY_MS); } long startTime = System.nanoTime(); assertNull(q.poll(timeoutMillis(), MILLISECONDS)); assertTrue(millisElapsedSince(startTime) >= timeoutMillis()); checkEmpty(q); } /** * Interrupted timed poll throws InterruptedException instead of * returning timeout status */ public void testInterruptedTimedPoll() throws InterruptedException { final BlockingQueue<Integer> q = populatedDeque(SIZE); final CountDownLatch aboutToWait = new CountDownLatch(1); Thread t = newStartedThread(new CheckedRunnable() { public void realRun() throws InterruptedException { long startTime = System.nanoTime(); for (int i = 0; i < SIZE; ++i) { assertEquals(i, (int) q.poll(LONG_DELAY_MS, MILLISECONDS)); } aboutToWait.countDown(); try { q.poll(LONG_DELAY_MS, MILLISECONDS); shouldThrow(); } catch (InterruptedException success) { assertTrue(millisElapsedSince(startTime) < LONG_DELAY_MS); } }}); aboutToWait.await(); waitForThreadToEnterWaitState(t, LONG_DELAY_MS); t.interrupt(); awaitTermination(t); checkEmpty(q); } /** * putFirst(null) throws NPE */ public void testPutFirstNull() throws InterruptedException { LinkedBlockingDeque q = new LinkedBlockingDeque(SIZE); try { q.putFirst(null); shouldThrow(); } catch (NullPointerException success) {} } /** * all elements successfully putFirst are contained */ public void testPutFirst() throws InterruptedException { LinkedBlockingDeque q = new LinkedBlockingDeque(SIZE); for (int i = 0; i < SIZE; ++i) { Integer x = new Integer(i); q.putFirst(x); assertTrue(q.contains(x)); } assertEquals(0, q.remainingCapacity()); } /** * putFirst blocks interruptibly if full */ public void testBlockingPutFirst() throws InterruptedException { final LinkedBlockingDeque q = new LinkedBlockingDeque(SIZE); final CountDownLatch pleaseInterrupt = new CountDownLatch(1); Thread t = newStartedThread(new CheckedRunnable() { public void realRun() throws InterruptedException { for (int i = 0; i < SIZE; ++i) q.putFirst(i); assertEquals(SIZE, q.size()); assertEquals(0, q.remainingCapacity()); Thread.currentThread().interrupt(); try { q.putFirst(99); shouldThrow(); } catch (InterruptedException success) {} assertFalse(Thread.interrupted()); pleaseInterrupt.countDown(); try { q.putFirst(99); shouldThrow(); } catch (InterruptedException success) {} assertFalse(Thread.interrupted()); }}); await(pleaseInterrupt); assertThreadStaysAlive(t); t.interrupt(); awaitTermination(t); assertEquals(SIZE, q.size()); assertEquals(0, q.remainingCapacity()); } /** * putFirst blocks interruptibly waiting for take when full */ public void testPutFirstWithTake() throws InterruptedException { final int capacity = 2; final LinkedBlockingDeque q = new LinkedBlockingDeque(capacity); final CountDownLatch pleaseTake = new CountDownLatch(1); final CountDownLatch pleaseInterrupt = new CountDownLatch(1); Thread t = newStartedThread(new CheckedRunnable() { public void realRun() throws InterruptedException { for (int i = 0; i < capacity; i++) q.putFirst(i); pleaseTake.countDown(); q.putFirst(86); pleaseInterrupt.countDown(); try { q.putFirst(99); shouldThrow(); } catch (InterruptedException success) {} assertFalse(Thread.interrupted()); }}); await(pleaseTake); assertEquals(0, q.remainingCapacity()); assertEquals(capacity - 1, q.take()); await(pleaseInterrupt); assertThreadStaysAlive(t); t.interrupt(); awaitTermination(t); assertEquals(0, q.remainingCapacity()); } /** * timed offerFirst times out if full and elements not taken */ public void testTimedOfferFirst() throws InterruptedException { final LinkedBlockingDeque q = new LinkedBlockingDeque(2); final CountDownLatch pleaseInterrupt = new CountDownLatch(1); Thread t = newStartedThread(new CheckedRunnable() { public void realRun() throws InterruptedException { q.putFirst(new Object()); q.putFirst(new Object()); long startTime = System.nanoTime(); assertFalse(q.offerFirst(new Object(), timeoutMillis(), MILLISECONDS)); assertTrue(millisElapsedSince(startTime) >= timeoutMillis()); pleaseInterrupt.countDown(); try { q.offerFirst(new Object(), 2 * LONG_DELAY_MS, MILLISECONDS); shouldThrow(); } catch (InterruptedException success) {} }}); await(pleaseInterrupt); assertThreadStaysAlive(t); t.interrupt(); awaitTermination(t); } /** * take retrieves elements in FIFO order */ public void testTakeFirst() throws InterruptedException { LinkedBlockingDeque q = populatedDeque(SIZE); for (int i = 0; i < SIZE; ++i) { assertEquals(i, q.takeFirst()); } } /** * takeFirst() blocks interruptibly when empty */ public void testTakeFirstFromEmptyBlocksInterruptibly() { final BlockingDeque q = new LinkedBlockingDeque(); final CountDownLatch threadStarted = new CountDownLatch(1); Thread t = newStartedThread(new CheckedRunnable() { public void realRun() { threadStarted.countDown(); try { q.takeFirst(); shouldThrow(); } catch (InterruptedException success) {} assertFalse(Thread.interrupted()); }}); await(threadStarted); assertThreadStaysAlive(t); t.interrupt(); awaitTermination(t); } /** * takeFirst() throws InterruptedException immediately if interrupted * before waiting */ public void testTakeFirstFromEmptyAfterInterrupt() { final BlockingDeque q = new LinkedBlockingDeque(); Thread t = newStartedThread(new CheckedRunnable() { public void realRun() { Thread.currentThread().interrupt(); try { q.takeFirst(); shouldThrow(); } catch (InterruptedException success) {} assertFalse(Thread.interrupted()); }}); awaitTermination(t); } /** * takeLast() blocks interruptibly when empty */ public void testTakeLastFromEmptyBlocksInterruptibly() { final BlockingDeque q = new LinkedBlockingDeque(); final CountDownLatch threadStarted = new CountDownLatch(1); Thread t = newStartedThread(new CheckedRunnable() { public void realRun() { threadStarted.countDown(); try { q.takeLast(); shouldThrow(); } catch (InterruptedException success) {} assertFalse(Thread.interrupted()); }}); await(threadStarted); assertThreadStaysAlive(t); t.interrupt(); awaitTermination(t); } /** * takeLast() throws InterruptedException immediately if interrupted * before waiting */ public void testTakeLastFromEmptyAfterInterrupt() { final BlockingDeque q = new LinkedBlockingDeque(); Thread t = newStartedThread(new CheckedRunnable() { public void realRun() { Thread.currentThread().interrupt(); try { q.takeLast(); shouldThrow(); } catch (InterruptedException success) {} assertFalse(Thread.interrupted()); }}); awaitTermination(t); } /** * takeFirst removes existing elements until empty, then blocks interruptibly */ public void testBlockingTakeFirst() throws InterruptedException { final LinkedBlockingDeque q = populatedDeque(SIZE); final CountDownLatch pleaseInterrupt = new CountDownLatch(1); Thread t = newStartedThread(new CheckedRunnable() { public void realRun() throws InterruptedException { for (int i = 0; i < SIZE; ++i) { assertEquals(i, q.takeFirst()); } Thread.currentThread().interrupt(); try { q.takeFirst(); shouldThrow(); } catch (InterruptedException success) {} assertFalse(Thread.interrupted()); pleaseInterrupt.countDown(); try { q.takeFirst(); shouldThrow(); } catch (InterruptedException success) {} assertFalse(Thread.interrupted()); }}); await(pleaseInterrupt); assertThreadStaysAlive(t); t.interrupt(); awaitTermination(t); } /** * timed pollFirst with zero timeout succeeds when non-empty, else times out */ public void testTimedPollFirst0() throws InterruptedException { LinkedBlockingDeque q = populatedDeque(SIZE); for (int i = 0; i < SIZE; ++i) { assertEquals(i, q.pollFirst(0, MILLISECONDS)); } assertNull(q.pollFirst(0, MILLISECONDS)); } /** * timed pollFirst with nonzero timeout succeeds when non-empty, else times out */ public void testTimedPollFirst() throws InterruptedException { LinkedBlockingDeque q = populatedDeque(SIZE); for (int i = 0; i < SIZE; ++i) { long startTime = System.nanoTime(); assertEquals(i, q.pollFirst(LONG_DELAY_MS, MILLISECONDS)); assertTrue(millisElapsedSince(startTime) < LONG_DELAY_MS); } long startTime = System.nanoTime(); assertNull(q.pollFirst(timeoutMillis(), MILLISECONDS)); assertTrue(millisElapsedSince(startTime) >= timeoutMillis()); checkEmpty(q); } /** * Interrupted timed pollFirst throws InterruptedException instead of * returning timeout status */ public void testInterruptedTimedPollFirst() throws InterruptedException { final LinkedBlockingDeque q = populatedDeque(SIZE); final CountDownLatch pleaseInterrupt = new CountDownLatch(1); Thread t = newStartedThread(new CheckedRunnable() { public void realRun() throws InterruptedException { long startTime = System.nanoTime(); for (int i = 0; i < SIZE; ++i) { assertEquals(i, q.pollFirst(LONG_DELAY_MS, MILLISECONDS)); } Thread.currentThread().interrupt(); try { q.pollFirst(LONG_DELAY_MS, MILLISECONDS); shouldThrow(); } catch (InterruptedException success) {} assertFalse(Thread.interrupted()); pleaseInterrupt.countDown(); try { q.pollFirst(LONG_DELAY_MS, MILLISECONDS); shouldThrow(); } catch (InterruptedException success) {} assertFalse(Thread.interrupted()); assertTrue(millisElapsedSince(startTime) < LONG_DELAY_MS); }}); await(pleaseInterrupt); assertThreadStaysAlive(t); t.interrupt(); awaitTermination(t); } /** * timed pollFirst before a delayed offerFirst fails; after offerFirst succeeds; * on interruption throws */ public void testTimedPollFirstWithOfferFirst() throws InterruptedException { final LinkedBlockingDeque q = new LinkedBlockingDeque(2); final CheckedBarrier barrier = new CheckedBarrier(2); Thread t = newStartedThread(new CheckedRunnable() { public void realRun() throws InterruptedException { long startTime = System.nanoTime(); assertNull(q.pollFirst(timeoutMillis(), MILLISECONDS)); assertTrue(millisElapsedSince(startTime) >= timeoutMillis()); barrier.await(); assertSame(zero, q.pollFirst(LONG_DELAY_MS, MILLISECONDS)); Thread.currentThread().interrupt(); try { q.pollFirst(LONG_DELAY_MS, MILLISECONDS); shouldThrow(); } catch (InterruptedException success) {} barrier.await(); try { q.pollFirst(LONG_DELAY_MS, MILLISECONDS); shouldThrow(); } catch (InterruptedException success) {} assertTrue(millisElapsedSince(startTime) < LONG_DELAY_MS); }}); barrier.await(); long startTime = System.nanoTime(); assertTrue(q.offerFirst(zero, LONG_DELAY_MS, MILLISECONDS)); assertTrue(millisElapsedSince(startTime) < LONG_DELAY_MS); barrier.await(); assertThreadStaysAlive(t); t.interrupt(); awaitTermination(t); } /** * putLast(null) throws NPE */ public void testPutLastNull() throws InterruptedException { LinkedBlockingDeque q = new LinkedBlockingDeque(SIZE); try { q.putLast(null); shouldThrow(); } catch (NullPointerException success) {} } /** * all elements successfully putLast are contained */ public void testPutLast() throws InterruptedException { LinkedBlockingDeque q = new LinkedBlockingDeque(SIZE); for (int i = 0; i < SIZE; ++i) { Integer x = new Integer(i); q.putLast(x); assertTrue(q.contains(x)); } assertEquals(0, q.remainingCapacity()); } /** * putLast blocks interruptibly if full */ public void testBlockingPutLast() throws InterruptedException { final LinkedBlockingDeque q = new LinkedBlockingDeque(SIZE); final CountDownLatch pleaseInterrupt = new CountDownLatch(1); Thread t = newStartedThread(new CheckedRunnable() { public void realRun() throws InterruptedException { for (int i = 0; i < SIZE; ++i) q.putLast(i); assertEquals(SIZE, q.size()); assertEquals(0, q.remainingCapacity()); Thread.currentThread().interrupt(); try { q.putLast(99); shouldThrow(); } catch (InterruptedException success) {} assertFalse(Thread.interrupted()); pleaseInterrupt.countDown(); try { q.putLast(99); shouldThrow(); } catch (InterruptedException success) {} assertFalse(Thread.interrupted()); }}); await(pleaseInterrupt); assertThreadStaysAlive(t); t.interrupt(); awaitTermination(t); assertEquals(SIZE, q.size()); assertEquals(0, q.remainingCapacity()); } /** * putLast blocks interruptibly waiting for take when full */ public void testPutLastWithTake() throws InterruptedException { final int capacity = 2; final LinkedBlockingDeque q = new LinkedBlockingDeque(capacity); final CountDownLatch pleaseTake = new CountDownLatch(1); final CountDownLatch pleaseInterrupt = new CountDownLatch(1); Thread t = newStartedThread(new CheckedRunnable() { public void realRun() throws InterruptedException { for (int i = 0; i < capacity; i++) q.putLast(i); pleaseTake.countDown(); q.putLast(86); pleaseInterrupt.countDown(); try { q.putLast(99); shouldThrow(); } catch (InterruptedException success) {} assertFalse(Thread.interrupted()); }}); await(pleaseTake); assertEquals(0, q.remainingCapacity()); assertEquals(0, q.take()); await(pleaseInterrupt); assertThreadStaysAlive(t); t.interrupt(); awaitTermination(t); assertEquals(0, q.remainingCapacity()); } /** * timed offerLast times out if full and elements not taken */ public void testTimedOfferLast() throws InterruptedException { final LinkedBlockingDeque q = new LinkedBlockingDeque(2); final CountDownLatch pleaseInterrupt = new CountDownLatch(1); Thread t = newStartedThread(new CheckedRunnable() { public void realRun() throws InterruptedException { q.putLast(new Object()); q.putLast(new Object()); long startTime = System.nanoTime(); assertFalse(q.offerLast(new Object(), timeoutMillis(), MILLISECONDS)); assertTrue(millisElapsedSince(startTime) >= timeoutMillis()); pleaseInterrupt.countDown(); try { q.offerLast(new Object(), 2 * LONG_DELAY_MS, MILLISECONDS); shouldThrow(); } catch (InterruptedException success) {} }}); await(pleaseInterrupt); assertThreadStaysAlive(t); t.interrupt(); awaitTermination(t); } /** * takeLast retrieves elements in FIFO order */ public void testTakeLast() throws InterruptedException { LinkedBlockingDeque q = populatedDeque(SIZE); for (int i = 0; i < SIZE; ++i) { assertEquals(SIZE - i - 1, q.takeLast()); } } /** * takeLast removes existing elements until empty, then blocks interruptibly */ public void testBlockingTakeLast() throws InterruptedException { final LinkedBlockingDeque q = populatedDeque(SIZE); final CountDownLatch pleaseInterrupt = new CountDownLatch(1); Thread t = newStartedThread(new CheckedRunnable() { public void realRun() throws InterruptedException { for (int i = 0; i < SIZE; ++i) { assertEquals(SIZE - i - 1, q.takeLast()); } Thread.currentThread().interrupt(); try { q.takeLast(); shouldThrow(); } catch (InterruptedException success) {} assertFalse(Thread.interrupted()); pleaseInterrupt.countDown(); try { q.takeLast(); shouldThrow(); } catch (InterruptedException success) {} assertFalse(Thread.interrupted()); }}); await(pleaseInterrupt); assertThreadStaysAlive(t); t.interrupt(); awaitTermination(t); } /** * timed pollLast with zero timeout succeeds when non-empty, else times out */ public void testTimedPollLast0() throws InterruptedException { LinkedBlockingDeque q = populatedDeque(SIZE); for (int i = 0; i < SIZE; ++i) { assertEquals(SIZE - i - 1, q.pollLast(0, MILLISECONDS)); } assertNull(q.pollLast(0, MILLISECONDS)); } /** * timed pollLast with nonzero timeout succeeds when non-empty, else times out */ public void testTimedPollLast() throws InterruptedException { LinkedBlockingDeque q = populatedDeque(SIZE); for (int i = 0; i < SIZE; ++i) { long startTime = System.nanoTime(); assertEquals(SIZE - i - 1, q.pollLast(LONG_DELAY_MS, MILLISECONDS)); assertTrue(millisElapsedSince(startTime) < LONG_DELAY_MS); } long startTime = System.nanoTime(); assertNull(q.pollLast(timeoutMillis(), MILLISECONDS)); assertTrue(millisElapsedSince(startTime) >= timeoutMillis()); checkEmpty(q); } /** * Interrupted timed pollLast throws InterruptedException instead of * returning timeout status */ public void testInterruptedTimedPollLast() throws InterruptedException { final LinkedBlockingDeque q = populatedDeque(SIZE); final CountDownLatch pleaseInterrupt = new CountDownLatch(1); Thread t = newStartedThread(new CheckedRunnable() { public void realRun() throws InterruptedException { long startTime = System.nanoTime(); for (int i = 0; i < SIZE; ++i) { assertEquals(SIZE - i - 1, q.pollLast(LONG_DELAY_MS, MILLISECONDS)); } Thread.currentThread().interrupt(); try { q.pollLast(LONG_DELAY_MS, MILLISECONDS); shouldThrow(); } catch (InterruptedException success) {} assertFalse(Thread.interrupted()); pleaseInterrupt.countDown(); try { q.pollLast(LONG_DELAY_MS, MILLISECONDS); shouldThrow(); } catch (InterruptedException success) {} assertFalse(Thread.interrupted()); assertTrue(millisElapsedSince(startTime) < LONG_DELAY_MS); }}); await(pleaseInterrupt); assertThreadStaysAlive(t); t.interrupt(); awaitTermination(t); checkEmpty(q); } /** * timed poll before a delayed offerLast fails; after offerLast succeeds; * on interruption throws */ public void testTimedPollWithOfferLast() throws InterruptedException { final LinkedBlockingDeque q = new LinkedBlockingDeque(2); final CheckedBarrier barrier = new CheckedBarrier(2); Thread t = newStartedThread(new CheckedRunnable() { public void realRun() throws InterruptedException { long startTime = System.nanoTime(); assertNull(q.poll(timeoutMillis(), MILLISECONDS)); assertTrue(millisElapsedSince(startTime) >= timeoutMillis()); barrier.await(); assertSame(zero, q.poll(LONG_DELAY_MS, MILLISECONDS)); Thread.currentThread().interrupt(); try { q.poll(LONG_DELAY_MS, MILLISECONDS); shouldThrow(); } catch (InterruptedException success) {} assertFalse(Thread.interrupted()); barrier.await(); try { q.poll(LONG_DELAY_MS, MILLISECONDS); shouldThrow(); } catch (InterruptedException success) {} assertFalse(Thread.interrupted()); assertTrue(millisElapsedSince(startTime) < LONG_DELAY_MS); }}); barrier.await(); long startTime = System.nanoTime(); assertTrue(q.offerLast(zero, LONG_DELAY_MS, MILLISECONDS)); assertTrue(millisElapsedSince(startTime) < LONG_DELAY_MS); barrier.await(); assertThreadStaysAlive(t); t.interrupt(); awaitTermination(t); } /** * element returns next element, or throws NSEE if empty */ public void testElement() { LinkedBlockingDeque q = populatedDeque(SIZE); for (int i = 0; i < SIZE; ++i) { assertEquals(i, q.element()); q.poll(); } try { q.element(); shouldThrow(); } catch (NoSuchElementException success) {} } /** * contains(x) reports true when elements added but not yet removed */ public void testContains() { LinkedBlockingDeque q = populatedDeque(SIZE); for (int i = 0; i < SIZE; ++i) { assertTrue(q.contains(new Integer(i))); q.poll(); assertFalse(q.contains(new Integer(i))); } } /** * clear removes all elements */ public void testClear() { LinkedBlockingDeque q = populatedDeque(SIZE); q.clear(); assertTrue(q.isEmpty()); assertEquals(0, q.size()); assertEquals(SIZE, q.remainingCapacity()); q.add(one); assertFalse(q.isEmpty()); assertTrue(q.contains(one)); q.clear(); assertTrue(q.isEmpty()); } /** * containsAll(c) is true when c contains a subset of elements */ public void testContainsAll() { LinkedBlockingDeque q = populatedDeque(SIZE); LinkedBlockingDeque p = new LinkedBlockingDeque(SIZE); for (int i = 0; i < SIZE; ++i) { assertTrue(q.containsAll(p)); assertFalse(p.containsAll(q)); p.add(new Integer(i)); } assertTrue(p.containsAll(q)); } /** * retainAll(c) retains only those elements of c and reports true if changed */ public void testRetainAll() { LinkedBlockingDeque q = populatedDeque(SIZE); LinkedBlockingDeque p = populatedDeque(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)); assertEquals(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) { LinkedBlockingDeque q = populatedDeque(SIZE); LinkedBlockingDeque p = populatedDeque(i); assertTrue(q.removeAll(p)); assertEquals(SIZE - i, q.size()); for (int j = 0; j < i; ++j) { Integer x = (Integer)(p.remove()); assertFalse(q.contains(x)); } } } /** * toArray contains all elements in FIFO order */ public void testToArray() throws InterruptedException { LinkedBlockingDeque q = populatedDeque(SIZE); Object[] o = q.toArray(); for (int i = 0; i < o.length; i++) assertSame(o[i], q.poll()); } /** * toArray(a) contains all elements in FIFO order */ public void testToArray2() { LinkedBlockingDeque<Integer> q = populatedDeque(SIZE); Integer[] ints = new Integer[SIZE]; Integer[] array = q.toArray(ints); assertSame(ints, array); for (int i = 0; i < ints.length; i++) assertSame(ints[i], q.remove()); } /** * toArray(incompatible array type) throws ArrayStoreException */ public void testToArray1_BadArg() { LinkedBlockingDeque q = populatedDeque(SIZE); try { q.toArray(new String[10]); shouldThrow(); } catch (ArrayStoreException success) {} } /** * iterator iterates through all elements */ public void testIterator() throws InterruptedException { LinkedBlockingDeque q = populatedDeque(SIZE); Iterator it = q.iterator(); int i; for (i = 0; it.hasNext(); i++) assertTrue(q.contains(it.next())); assertEquals(i, SIZE); assertIteratorExhausted(it); it = q.iterator(); for (i = 0; it.hasNext(); i++) assertEquals(it.next(), q.take()); assertEquals(i, SIZE); assertIteratorExhausted(it); } /** * iterator of empty collection has no elements */ public void testEmptyIterator() { Deque c = new LinkedBlockingDeque(); assertIteratorExhausted(c.iterator()); assertIteratorExhausted(c.descendingIterator()); } /** * iterator.remove removes current element */ public void testIteratorRemove() { final LinkedBlockingDeque q = new LinkedBlockingDeque(3); q.add(two); q.add(one); q.add(three); Iterator it = q.iterator(); it.next(); it.remove(); it = q.iterator(); assertSame(it.next(), one); assertSame(it.next(), three); assertFalse(it.hasNext()); } /** * iterator ordering is FIFO */ public void testIteratorOrdering() { final LinkedBlockingDeque q = new LinkedBlockingDeque(3); q.add(one); q.add(two); q.add(three); assertEquals(0, q.remainingCapacity()); int k = 0; for (Iterator it = q.iterator(); it.hasNext();) { assertEquals(++k, it.next()); } assertEquals(3, k); } /** * Modifications do not cause iterators to fail */ public void testWeaklyConsistentIteration() { final LinkedBlockingDeque q = new LinkedBlockingDeque(3); q.add(one); q.add(two); q.add(three); for (Iterator it = q.iterator(); it.hasNext();) { q.remove(); it.next(); } assertEquals(0, q.size()); } /** * Descending iterator iterates through all elements */ public void testDescendingIterator() { LinkedBlockingDeque q = populatedDeque(SIZE); int i = 0; Iterator it = q.descendingIterator(); while (it.hasNext()) { assertTrue(q.contains(it.next())); ++i; } assertEquals(i, SIZE); assertFalse(it.hasNext()); try { it.next(); shouldThrow(); } catch (NoSuchElementException success) {} } /** * Descending iterator ordering is reverse FIFO */ public void testDescendingIteratorOrdering() { final LinkedBlockingDeque q = new LinkedBlockingDeque(); for (int iters = 0; iters < 100; ++iters) { q.add(new Integer(3)); q.add(new Integer(2)); q.add(new Integer(1)); int k = 0; for (Iterator it = q.descendingIterator(); it.hasNext();) { assertEquals(++k, it.next()); } assertEquals(3, k); q.remove(); q.remove(); q.remove(); } } /** * descendingIterator.remove removes current element */ public void testDescendingIteratorRemove() { final LinkedBlockingDeque q = new LinkedBlockingDeque(); for (int iters = 0; iters < 100; ++iters) { q.add(new Integer(3)); q.add(new Integer(2)); q.add(new Integer(1)); Iterator it = q.descendingIterator(); assertEquals(it.next(), new Integer(1)); it.remove(); assertEquals(it.next(), new Integer(2)); it = q.descendingIterator(); assertEquals(it.next(), new Integer(2)); assertEquals(it.next(), new Integer(3)); it.remove(); assertFalse(it.hasNext()); q.remove(); } } /** * toString contains toStrings of elements */ public void testToString() { LinkedBlockingDeque q = populatedDeque(SIZE); String s = q.toString(); for (int i = 0; i < SIZE; ++i) { assertTrue(s.contains(String.valueOf(i))); } } /** * offer transfers elements across Executor tasks */ public void testOfferInExecutor() { final LinkedBlockingDeque q = new LinkedBlockingDeque(2); q.add(one); q.add(two); final CheckedBarrier threadsStarted = new CheckedBarrier(2); final ExecutorService executor = Executors.newFixedThreadPool(2); try (PoolCleaner cleaner = cleaner(executor)) { executor.execute(new CheckedRunnable() { public void realRun() throws InterruptedException { assertFalse(q.offer(three)); threadsStarted.await(); assertTrue(q.offer(three, LONG_DELAY_MS, MILLISECONDS)); assertEquals(0, q.remainingCapacity()); }}); executor.execute(new CheckedRunnable() { public void realRun() throws InterruptedException { threadsStarted.await(); assertSame(one, q.take()); }}); } } /** * timed poll retrieves elements across Executor threads */ public void testPollInExecutor() { final LinkedBlockingDeque q = new LinkedBlockingDeque(2); final CheckedBarrier threadsStarted = new CheckedBarrier(2); final ExecutorService executor = Executors.newFixedThreadPool(2); try (PoolCleaner cleaner = cleaner(executor)) { executor.execute(new CheckedRunnable() { public void realRun() throws InterruptedException { assertNull(q.poll()); threadsStarted.await(); assertSame(one, q.poll(LONG_DELAY_MS, MILLISECONDS)); checkEmpty(q); }}); executor.execute(new CheckedRunnable() { public void realRun() throws InterruptedException { threadsStarted.await(); q.put(one); }}); } } /** * A deserialized serialized deque has same elements in same order */ public void testSerialization() throws Exception { Queue x = populatedDeque(SIZE); Queue y = serialClone(x); assertNotSame(y, x); assertEquals(x.size(), y.size()); assertEquals(x.toString(), y.toString()); assertTrue(Arrays.equals(x.toArray(), y.toArray())); while (!x.isEmpty()) { assertFalse(y.isEmpty()); assertEquals(x.remove(), y.remove()); } assertTrue(y.isEmpty()); } /** * drainTo(c) empties deque into another collection c */ public void testDrainTo() { LinkedBlockingDeque q = populatedDeque(SIZE); ArrayList l = new ArrayList(); q.drainTo(l); assertEquals(0, q.size()); assertEquals(SIZE, l.size()); for (int i = 0; i < SIZE; ++i) assertEquals(l.get(i), new Integer(i)); q.add(zero); q.add(one); assertFalse(q.isEmpty()); assertTrue(q.contains(zero)); assertTrue(q.contains(one)); l.clear(); q.drainTo(l); assertEquals(0, q.size()); assertEquals(2, l.size()); for (int i = 0; i < 2; ++i) assertEquals(l.get(i), new Integer(i)); } /** * drainTo empties full deque, unblocking a waiting put. */ public void testDrainToWithActivePut() throws InterruptedException { final LinkedBlockingDeque q = populatedDeque(SIZE); Thread t = new Thread(new CheckedRunnable() { public void realRun() throws InterruptedException { q.put(new Integer(SIZE + 1)); }}); t.start(); ArrayList l = new ArrayList(); q.drainTo(l); assertTrue(l.size() >= SIZE); for (int i = 0; i < SIZE; ++i) assertEquals(l.get(i), new Integer(i)); t.join(); assertTrue(q.size() + l.size() >= SIZE); } /** * drainTo(c, n) empties first min(n, size) elements of queue into c */ public void testDrainToN() { LinkedBlockingDeque q = new LinkedBlockingDeque(); for (int i = 0; i < SIZE + 2; ++i) { for (int j = 0; j < SIZE; j++) assertTrue(q.offer(new Integer(j))); ArrayList l = new ArrayList(); q.drainTo(l, i); int k = (i < SIZE) ? i : SIZE; assertEquals(k, l.size()); assertEquals(SIZE - k, q.size()); for (int j = 0; j < k; ++j) assertEquals(l.get(j), new Integer(j)); do {} while (q.poll() != null); } } /** * remove(null), contains(null) always return false */ public void testNeverContainsNull() { Deque<?>[] qs = { new LinkedBlockingDeque<Object>(), populatedDeque(2), }; for (Deque<?> q : qs) { assertFalse(q.contains(null)); assertFalse(q.remove(null)); assertFalse(q.removeFirstOccurrence(null)); assertFalse(q.removeLastOccurrence(null)); } } }