public static void main(String[] args) {
LinkedList books = new LinkedList();
// 将字符串元素加入队列的尾部
books.offer("疯狂Java讲义");
// 将一个字符串元素加入栈的顶部
books.push("轻量级Java EE企业应用实战");
// 将字符串元素添加到队列的头部（相当于栈的顶部）
books.offerFirst("疯狂Android讲义");
// 以List的方式（按索引访问的方式）来遍历集合元素
for (int i = 0; i < books.size(); i++) {
System.out.println("遍历中：" + books.get(i));
}
// 访问、并不删除栈顶的元素
System.out.println(books.peekFirst());
// 访问、并不删除队列的最后一个元素
System.out.println(books.peekLast());
// 将栈顶的元素弹出“栈”
System.out.println(books.pop());
// 下面输出将看到队列中第一个元素被删除
System.out.println(books);
// 访问、并删除队列的最后一个元素
System.out.println(books.pollLast());
// 下面输出：[轻量级Java EE企业应用实战]
System.out.println(books);
}
void startIdleState() {
lock.lock();
try {
final Thread currentThread = Thread.currentThread();
final Thread currentIdleThread = threadsRequestingIdle.peekFirst();
if (currentIdleThread == currentThread) {
assert idleStateCount > 0;
++idleStateCount;
assert idleStateCount > 0;
return;
}
threadsRequestingIdle.add(currentThread);
while ((activitiyCount > 0) || (threadsRequestingIdle.getFirst() != currentThread))
condition.awaitUninterruptibly();
assert idleStateCount == 0;
assert activitiyCount == 0;
assert threadsRequestingIdle.getFirst() == currentThread;
idleStateCount = 1;
} finally {
lock.unlock();
}
}
/**
* Replaces the entire stack with this fragment.
*
* @param args Arguments to be set on the fragment using {@link
* Fragment#setArguments(android.os.Bundle)}.
*/
public void replace(Class<?> fragment, String tag, Bundle args) {
Fragment first = stack.peekFirst();
if (first != null && tag.equals(first.getTag())) {
if (stack.size() > 1) {
ensureTransaction();
fragmentTransaction.setCustomAnimations(popStackEnterAnimation, popStackExitAnimation);
while (stack.size() > 1) {
removeFragment(stack.pollLast());
}
attachFragment(stack.peek(), tag);
}
return;
}
Fragment f = fragmentManager.findFragmentByTag(tag);
if (f == null) {
f = Fragment.instantiate(activity, fragment.getName(), args);
}
ensureTransaction();
fragmentTransaction.setCustomAnimations(enterAnimation, exitAnimation);
clear();
attachFragment(f, tag);
stack.add(f);
topLevelTags.add(tag);
}
public T pop() {
if (!buf.isEmpty()) {
T ret = buf.peekFirst();
buf.clear();
isBacktracking = true;
return ret;
}
throw new IllegalStateException("Can't pop an empty ringbuffer");
}
public Vertex(LinkedList<Character> entrada, ArrayList<Vertex> destiny) {
consecutivo = destiny.size();
destiny.add(this);
value = entrada.pollFirst();
if (entrada.isEmpty() || entrada.peekFirst() != '(') {
sons = new DLL();
} else {
entrada.pollFirst();
Vertex actual = new Vertex(entrada, destiny);
actual.sons.add(this);
sons = new DLL(actual);
while (entrada.peekFirst() == ',') {
entrada.pollFirst();
actual = new Vertex(entrada, destiny);
actual.sons.add(this);
sons.add(actual);
}
entrada.pollFirst();
}
}
public static void main(String a[]) {
LinkedList<String> arrl = new LinkedList<String>();
arrl.add("First");
arrl.add("Second");
arrl.add("Third");
arrl.add("Random");
System.out.println("First Element: " + arrl.element());
System.out.println("First Element: " + arrl.getFirst());
System.out.println("First Element: " + arrl.peek());
System.out.println("First Element: " + arrl.peekFirst());
}
public void clear() {
Fragment first = stack.peekFirst();
for (Fragment f : stack) {
if (f == first) {
detachFragment(f);
} else {
removeFragment(f);
}
}
stack.clear();
}
void endAllowingFileScopeRequests() {
lock.lock();
try {
final Thread currentThread = Thread.currentThread();
final Thread currentIdleThread = threadsRequestingIdle.peekFirst();
assert currentThread == currentIdleThread;
assert allowFileScopeRequests;
while (activitiyCount > 0) condition.awaitUninterruptibly();
allowFileScopeRequests = false;
} finally {
lock.unlock();
}
}
void startAllowingFileScopeRequests() {
lock.lock();
try {
final Thread currentThread = Thread.currentThread();
final Thread currentIdleThread = threadsRequestingIdle.peekFirst();
assert currentThread == currentIdleThread;
assert !allowFileScopeRequests;
allowFileScopeRequests = true;
condition.signalAll();
} finally {
lock.unlock();
}
}
/**
* add
*
* @param historyList
* @param maxHistoryLength max. length of history or HISTORY_LENGTH_INFINTE
* @param direction history direction order
* @param addEntry
*/
private static void add(
LinkedList<String> historyList, int maxHistoryLength, Directions direction, String addEntry) {
switch (direction) {
case ASCENDING:
{
String lastEntry = historyList.peekLast();
if ((lastEntry == null) || !lastEntry.equals(addEntry)) {
historyList.add(addEntry);
while (historyList.size() > maxHistoryLength) {
historyList.removeFirst();
}
}
}
break;
case DESCENDING:
{
String firstEntry = historyList.peekFirst();
if ((firstEntry == null) || !firstEntry.equals(addEntry)) {
historyList.addFirst(firstEntry);
while (historyList.size() > maxHistoryLength) {
historyList.removeLast();
}
}
}
break;
case SORTED:
{
boolean existsFlag = false;
for (String entry : historyList) {
if (entry.equals(addEntry)) {
existsFlag = true;
break;
}
}
if (!existsFlag) {
historyList.addFirst(addEntry);
Collections.sort(
historyList,
new Comparator<String>() {
public int compare(String data0, String data1) {
return data0.compareTo(data1);
}
});
while (historyList.size() > maxHistoryLength) {
historyList.removeLast();
}
}
}
break;
}
}
private static Map<IProjectStage, List<IProjectStageSkill>> extractStageToSkillMap(
List<IProjectStage> stages, List<IProjectStageSkill> skillsList) {
Map<IProjectStage, List<IProjectStageSkill>> stageToSkillListMap = Maps.newHashMap();
LinkedList<IProjectStageSkill> skillListCopy = Lists.newLinkedList(skillsList);
for (IProjectStage stage : stages) {
Set<IProjectStageSkill> skillSet = stage.getProjectStageSkills();
List<IProjectStageSkill> entryList = Lists.newLinkedList();
while (skillSet.contains(skillListCopy.peekFirst())) {
entryList.add(skillListCopy.pollFirst());
}
stageToSkillListMap.put(stage, entryList);
}
return stageToSkillListMap;
}
/** 测试LinkedList以双向链表的使用方法 */
private static void testLinkedListDeque() {
System.out.println(
"Test methods: addFirst(object), addLast(object), offerFirst(), offerLast(), getFirst(object), getLast(object), pollFirst(), pollLast(), peekFirst(), peekLast(), removeFirst(), removeLast()");
// 将 “abcdefg”初始化到LinkedList中
LinkedList<String> list = new LinkedList<String>();
// addFirst/addLast 没有返回值、offerFirst/offerLast返回true、内部都是调用Entry.addBefore()来添加的
list.addFirst("c");
list.offerFirst("b");
list.offerFirst("a");
list.addLast("d");
list.addLast("e");
list.offerLast("f");
printList(list);
/* 相同：
* getFirst/getLast、peekFirst/peekLast方法都是获取第一个元素、
* 不同：
* getXXX方法在list的size为0抛出异常、
* peekXX方法在list的size为0返回null、
*/
printStr("list getFirst() obtains element: " + list.getFirst());
printStr("list peekFirst() obtains element: " + list.peekFirst());
printStr("list getLast() obtains element: " + list.getLast());
printStr("list peekLast() obtains element: " + list.peekLast());
printList(list);
/*
* 相同：
* pollXXX、removeXXX都是获取第一个元素、并且将此元素从list中移除
* 不同：
* removeXXX方法在list的size为0抛出异常、
* pollXXX方法在list的size为0返回null、
*/
printStr(list.pollFirst());
printStr(list.removeFirst());
printList(list);
printStr(list.pollLast());
printStr(list.removeLast());
printList(list);
}
/** Removes all added fragments and clears the stack. */
public void destroy() {
ensureTransaction();
fragmentTransaction.setCustomAnimations(enterAnimation, exitAnimation);
final Fragment topFragment = stack.peekFirst();
for (Fragment f : stack) {
if (f != topFragment) {
removeFragment(f);
}
}
stack.clear();
for (String tag : topLevelTags) {
removeFragment(fragmentManager.findFragmentByTag(tag));
}
fragmentTransaction.commitAllowingStateLoss();
fragmentTransaction = null;
}
void endIdleState() {
lock.lock();
try {
final Thread currentThread = Thread.currentThread();
assert currentThread == threadsRequestingIdle.getFirst();
assert !allowFileScopeRequests;
assert idleStateCount > 0;
assert activitiyCount == 0;
--idleStateCount;
assert idleStateCount >= 0;
if (idleStateCount == 0) {
threadsRequestingIdle.remove();
assert currentThread != threadsRequestingIdle.peekFirst();
condition.signalAll();
}
} finally {
lock.unlock();
}
}
/**
* Updates the snake's position and size.
*
* @return Tile tile that the head moved into.
*/
private TileType updateSnake() {
/*
* Here we peek at the next direction rather than polling it. While
* not game breaking, polling the direction here causes a small bug
* where the snake's direction will change after a game over (though
* it will not move).
*/
Direction direction = directions.peekFirst();
/*
* Here we calculate the new point that the snake's head will be at
* after the update.
*/
Point head = new Point(snake.peekFirst());
switch (direction) {
case North:
head.y--;
break;
case South:
head.y++;
break;
case West:
head.x--;
break;
case East:
head.x++;
break;
}
/*
* If the snake has moved out of bounds ('hit' a wall), we can just
* return that it's collided with itself, as both cases are handled
* identically.
*/
if (head.x < 0
|| head.x >= BoardPanel.COL_COUNT
|| head.y < 0
|| head.y >= BoardPanel.ROW_COUNT) {
return TileType.SnakeBody; // Pretend we collided with our body.
}
/*
* Here we get the tile that was located at the new head position and
* remove the tail from of the snake and the board if the snake is
* long enough, and the tile it moved onto is not a fruit.
*
* If the tail was removed, we need to retrieve the old tile again
* incase the tile we hit was the tail piece that was just removed
* to prevent a false game over.
*/
TileType old = board.getTile(head.x, head.y);
if (old != TileType.Fruit && snake.size() > MIN_SNAKE_LENGTH) {
Point tail = snake.removeLast();
board.setTile(tail, null);
old = board.getTile(head.x, head.y);
}
/*
* Update the snake's position on the board if we didn't collide with
* our tail:
*
* 1. Set the old head position to a body tile.
* 2. Add the new head to the snake.
* 3. Set the new head position to a head tile.
*
* If more than one direction is in the queue, poll it to read new
* input.
*/
if (old != TileType.SnakeBody) {
board.setTile(snake.peekFirst(), TileType.SnakeBody);
snake.push(head);
board.setTile(head, TileType.SnakeHead);
if (directions.size() > 1) {
directions.poll();
}
}
return old;
}
/**
* Finally, synchronize our history with the Leader.
*
* @param newLeaderZxid
* @throws IOException
* @throws InterruptedException
*/
protected void syncWithLeader(long newLeaderZxid) throws IOException, InterruptedException {
QuorumPacket ack = new QuorumPacket(Leader.ACK, 0, null);
QuorumPacket qp = new QuorumPacket();
long newEpoch = ZxidUtils.getEpochFromZxid(newLeaderZxid);
readPacket(qp);
LinkedList<Long> packetsCommitted = new LinkedList<Long>();
LinkedList<PacketInFlight> packetsNotCommitted = new LinkedList<PacketInFlight>();
synchronized (zk) {
if (qp.getType() == Leader.DIFF) {
LOG.info("Getting a diff from the leader 0x" + Long.toHexString(qp.getZxid()));
} else if (qp.getType() == Leader.SNAP) {
LOG.info("Getting a snapshot from leader");
// The leader is going to dump the database
// clear our own database and read
zk.getZKDatabase().clear();
zk.getZKDatabase().deserializeSnapshot(leaderIs);
String signature = leaderIs.readString("signature");
if (!signature.equals("BenWasHere")) {
LOG.error("Missing signature. Got " + signature);
throw new IOException("Missing signature");
}
zk.getZKDatabase().commit();
zk.getZKDatabase().getM2mData().clear();
} else if (qp.getType() == Leader.TRUNC) {
// we need to truncate the log to the lastzxid of the leader
LOG.warn(
"Truncating log to get in sync with the leader 0x" + Long.toHexString(qp.getZxid()));
boolean truncated = zk.getZKDatabase().truncateLog(qp.getZxid());
if (!truncated) {
// not able to truncate the log
LOG.error("Not able to truncate the log " + Long.toHexString(qp.getZxid()));
System.exit(13);
}
} else {
LOG.error("Got unexpected packet from leader " + qp.getType() + " exiting ... ");
System.exit(13);
}
zk.getZKDatabase().setlastProcessedZxid(qp.getZxid());
zk.createSessionTracker();
long lastQueued = 0;
// in V1.0 we take a snapshot when we get the NEWLEADER message, but
// in pre V1.0
// we take the snapshot at the UPDATE, since V1.0 also gets the
// UPDATE (after the NEWLEADER)
// we need to make sure that we don't take the snapshot twice.
boolean snapshotTaken = false;
// we are now going to start getting transactions to apply followed
// by an UPTODATE
outerLoop:
while (self.isRunning()) {
readPacket(qp);
switch (qp.getType()) {
case Leader.PROPOSAL:
PacketInFlight pif = new PacketInFlight();
pif.hdr = new M2mTxnHeader();
pif.rec = M2mSerializeUtils.deserializeTxn(qp.getData(), pif.hdr);
if (pif.hdr.getZxid() != lastQueued + 1) {
LOG.warn(
"Got zxid 0x"
+ Long.toHexString(pif.hdr.getZxid())
+ " expected 0x"
+ Long.toHexString(lastQueued + 1));
}
lastQueued = pif.hdr.getZxid();
packetsNotCommitted.add(pif);
break;
case Leader.COMMIT:
if (!snapshotTaken) {
pif = packetsNotCommitted.peekFirst();
if (pif.hdr.getZxid() != qp.getZxid()) {
LOG.warn(
"Committing " + qp.getZxid() + ", but next proposal is " + pif.hdr.getZxid());
} else {
zk.processTxn(pif.hdr, pif.rec);
packetsNotCommitted.remove();
}
} else {
packetsCommitted.add(qp.getZxid());
}
break;
case Leader.INFORM:
/*
* Only observer get this type of packet. We treat this as
* receiving PROPOSAL and COMMMIT.
*/
PacketInFlight packet = new PacketInFlight();
packet.hdr = new M2mTxnHeader();
packet.rec = M2mSerializeUtils.deserializeTxn(qp.getData(), packet.hdr);
// Log warning message if txn comes out-of-order
if (packet.hdr.getZxid() != lastQueued + 1) {
LOG.warn(
"Got zxid 0x"
+ Long.toHexString(packet.hdr.getZxid())
+ " expected 0x"
+ Long.toHexString(lastQueued + 1));
}
lastQueued = packet.hdr.getZxid();
if (!snapshotTaken) {
// Apply to db directly if we haven't taken the snapshot
zk.processTxn(packet.hdr, packet.rec);
} else {
packetsNotCommitted.add(packet);
packetsCommitted.add(qp.getZxid());
}
break;
case Leader.UPTODATE:
if (!snapshotTaken) { // true for the pre v1.0 case
zk.takeSnapshot();
self.setCurrentEpoch(newEpoch);
}
self.cnxnFactory.addZooKeeperServer(self.getHandleIp(), zk);
break outerLoop;
case Leader.NEWLEADER: // it will be NEWLEADER in v1.0
// Create updatingEpoch file and remove it after current
// epoch is set. QuorumPeer.loadDataBase() uses this file to
// detect the case where the server was terminated after
// taking a snapshot but before setting the current epoch.
// File updating = new
// File(self.getTxnFactory().getSnapDir(),
// QuorumPeer.UPDATING_EPOCH_FILENAME);
// if (!updating.exists() && !updating.createNewFile()) {
// throw new IOException("Failed to create "
// + updating.toString());
// }
// zk.takeSnapshot();
// self.setCurrentEpoch(newEpoch);
// if (!updating.delete()) {
// throw new IOException("Failed to delete "
// + updating.toString());
// }
snapshotTaken = true;
writePacket(new QuorumPacket(Leader.ACK, newLeaderZxid, null), true);
break;
}
}
}
ack.setZxid(ZxidUtils.makeZxid(newEpoch, 0));
writePacket(ack, true);
sock.setSoTimeout(self.tickTime * self.syncLimit);
zk.startup();
/*
* Update the election vote here to ensure that all members of the
* ensemble report the same vote to new servers that start up and send
* leader election notifications to the ensemble.
*
* @see https://issues.apache.org/jira/browse/ZOOKEEPER-1732
*/
self.updateElectionVote(newEpoch);
// We need to log the stuff that came in between the snapshot and the
// uptodate
if (zk instanceof FollowerZooKeeperServer) {
FollowerZooKeeperServer fzk = (FollowerZooKeeperServer) zk;
for (PacketInFlight p : packetsNotCommitted) {
fzk.logRequest(p.hdr, p.rec);
}
for (Long zxid : packetsCommitted) {
fzk.commit(zxid);
}
} else {
// New server type need to handle in-flight packets
throw new UnsupportedOperationException("Unknown server type");
}
}
@Override
public Solution getBest() {
return solutions.peekFirst();
}
public MockCatalogBuilder commit() {
if (!featureTypes.isEmpty() || !coverages.isEmpty()) {
if (!featureTypes.isEmpty()) {
DataStoreInfo ds = dataStores.peekLast();
expect(catalog.getResourcesByStore(ds, FeatureTypeInfo.class))
.andReturn(featureTypes)
.anyTimes();
expect(catalog.getResourcesByStore(ds, ResourceInfo.class))
.andReturn((List) featureTypes)
.anyTimes();
expect(catalog.getFeatureTypesByDataStore(ds)).andReturn(featureTypes).anyTimes();
}
if (!coverages.isEmpty()) {
CoverageStoreInfo cs = coverageStores.peekLast();
expect(catalog.getResourcesByStore(cs, CoverageInfo.class)).andReturn(coverages).anyTimes();
expect(catalog.getResourcesByStore(cs, ResourceInfo.class))
.andReturn((List) coverages)
.anyTimes();
expect(catalog.getCoveragesByCoverageStore(cs)).andReturn(coverages).anyTimes();
}
// clear out local lists but push up to be included when this workspace is complete
featureTypesByNamespace.addAll(featureTypes);
featureTypes = new LinkedList<FeatureTypeInfo>();
coveragesByNamespace.addAll(coverages);
coverages = new LinkedList<CoverageInfo>();
} else if (!dataStores.isEmpty() || !coverageStores.isEmpty()) {
WorkspaceInfo ws = workspaces.peekLast();
NamespaceInfo ns = namespaces.peekLast();
expect(catalog.getStoresByWorkspace(ws.getName(), DataStoreInfo.class))
.andReturn(dataStores)
.anyTimes();
expect(catalog.getStoresByWorkspace(ws, DataStoreInfo.class))
.andReturn(dataStores)
.anyTimes();
expect(catalog.getDataStoresByWorkspace(ws.getName())).andReturn(dataStores).anyTimes();
expect(catalog.getDataStoresByWorkspace(ws)).andReturn(dataStores).anyTimes();
expect(catalog.getStoresByWorkspace(ws.getName(), CoverageStoreInfo.class))
.andReturn(coverageStores)
.anyTimes();
expect(catalog.getStoresByWorkspace(ws, CoverageStoreInfo.class))
.andReturn(coverageStores)
.anyTimes();
expect(catalog.getCoverageStoresByWorkspace(ws.getName()))
.andReturn(coverageStores)
.anyTimes();
expect(catalog.getCoverageStoresByWorkspace(ws)).andReturn(coverageStores).anyTimes();
List<StoreInfo> l = new LinkedList<StoreInfo>(dataStores);
l.addAll(coverageStores);
expect(catalog.getStoresByWorkspace(ws.getName(), StoreInfo.class)).andReturn(l).anyTimes();
expect(catalog.getStoresByWorkspace(ws, StoreInfo.class)).andReturn(l).anyTimes();
// add all the resources for this workspace
List<ResourceInfo> m = new LinkedList(featureTypesByNamespace);
m.addAll(coveragesByNamespace);
expect(catalog.getResourcesByNamespace(ns, ResourceInfo.class)).andReturn(m).anyTimes();
// expect(catalog.getResourcesByNamespace(ns.getPrefix(),
// ResourceInfo.class)).andReturn(m).anyTimes();
expect(catalog.getResourcesByNamespace(ns, FeatureTypeInfo.class))
.andReturn(featureTypesByNamespace)
.anyTimes();
// expect(catalog.getResourcesByNamespace(ns.getPrefix(), FeatureTypeInfo.class))
// .andReturn(featureTypesByNamespace).anyTimes();
expect(catalog.getResourcesByNamespace(ns, CoverageInfo.class))
.andReturn(coveragesByNamespace)
.anyTimes();
// expect(catalog.getResourcesByNamespace(ns.getPrefix(), CoverageInfo.class))
// .andReturn(coveragesByNamespace).anyTimes();
dataStoresAll.addAll(dataStores);
dataStores = new LinkedList();
coverageStoresAll.addAll(coverageStores);
coverageStores = new LinkedList();
featureTypesAll.addAll(featureTypesByNamespace);
featureTypesByNamespace = new LinkedList();
coveragesAll.addAll(coveragesByNamespace);
coveragesByNamespace = new LinkedList();
} else if (!workspaces.isEmpty()) {
// all the resources
List<ResourceInfo> l = new LinkedList<ResourceInfo>(featureTypesAll);
l.addAll(coveragesAll);
expect(catalog.getResources(ResourceInfo.class)).andReturn(l).anyTimes();
expect(catalog.getResources(FeatureTypeInfo.class)).andReturn(featureTypesAll).anyTimes();
expect(catalog.getResources(CoverageInfo.class)).andReturn(coverages).anyTimes();
expect(catalog.getFeatureTypes()).andReturn(featureTypesAll).anyTimes();
expect(catalog.getCoverages()).andReturn(coveragesAll).anyTimes();
// add all the stores
List<StoreInfo> m = new LinkedList<StoreInfo>(dataStoresAll);
m.addAll(coverageStoresAll);
expect(catalog.getStores(StoreInfo.class)).andReturn(m).anyTimes();
expect(catalog.getStores(DataStoreInfo.class)).andReturn(dataStoresAll).anyTimes();
expect(catalog.getStores(CoverageStoreInfo.class)).andReturn(coverageStoresAll).anyTimes();
// add all the styles
expect(catalog.getStyles()).andReturn(styles).anyTimes();
// add all the layer groups
expect(catalog.getLayerGroups()).andReturn(layerGroups).anyTimes();
// add all the workspaces/namespaces
expect(catalog.getWorkspaces()).andReturn(workspaces).anyTimes();
expect(catalog.getNamespaces()).andReturn(namespaces).anyTimes();
// default workspace/namespace
expect(catalog.getDefaultWorkspace()).andReturn(workspaces.peekFirst()).anyTimes();
expect(catalog.getDefaultNamespace()).andReturn(namespaces.peekFirst()).anyTimes();
replay(catalog);
featureTypesAll = new LinkedList();
coveragesAll = new LinkedList();
dataStoresAll = new LinkedList();
coverageStoresAll = new LinkedList();
styles = new LinkedList();
workspaces = new LinkedList();
namespaces = new LinkedList();
}
return this;
}