java.util.Queue#offer ( )源码实例Demo

/**
 * BFS. O(V) Time. O(V) Space.
 * Use map<Integer, UndirectedGraphNode> to store cloned new graph nodes.
 * For each visit, connect the node with neighboring nodes.
 * If neighboring nodes not in new graph yet, need to create them.
 * Visit:
 * Check whether current label is in new graph:
 * | If not, create a new node with current label and put in map.
 * If neighbors exist:
 * | For each neighbor:
 * |   If its not visited, add it to queue and create a new node.
 * |   Connect current node with this neighbor.
 */
public UndirectedGraphNode cloneGraph2(UndirectedGraphNode node) {
  if (node == null) {
    return null;
  }
  Queue<UndirectedGraphNode> q = new ArrayDeque<>();
  Map<Integer, UndirectedGraphNode> cloned = new HashMap<>(); // Cloned graph nodes.
  q.offer(node);
  cloned.put(node.label, new UndirectedGraphNode(node.label));
  while (!q.isEmpty()) {
    UndirectedGraphNode cur = q.poll();
    if (!cloned.containsKey(cur.label))
      cloned.put(cur.label, new UndirectedGraphNode(cur.label)); // Put in map to set as visited.
    if (cur.neighbors != null) {
      for (UndirectedGraphNode n : cur.neighbors) {
        if (!cloned.containsKey(n.label)) { // Add all unvisited neighbors to the queue.
          q.offer(n);
          cloned.put(n.label, new UndirectedGraphNode(n.label));
        }
        // Connect cloned node with every neighbor. No matter visited or not.
        cloned.get(cur.label).neighbors.add(cloned.get(n.label));
      }
    }
  }
  return cloned.get(node.label);
}
 

public static void main(String[] args) {
    Queue<String> queue = new LinkedList<String>();

    queue.offer("Hello");
    queue.offer("world!");
    queue.offer("您好！");

    System.out.println("使用offer()之后队列的长度：" + queue.size());
    System.out.println("使用peek()取出第一个元素：  " + queue.peek());
    System.out.println("使用element()取出第一个元素：  " + queue.element());
    System.out.println("使用peek/element之后队列的长度：  " + queue.size());
    System.out.println("使用poll()循环取出并删除元素：" + queue.poll());
    String str;
    while ((str = queue.poll()) != null) {
        System.out.print(" " + str);
    }
    System.out.println();
    System.out.print("使用poll()后队列的长度：" + queue.size());
}
 

@SuppressWarnings({ "rawtypes" })
private void traverseFragmentChildren(Queue<View> views) {
    while (!views.isEmpty()) {
        View view = views.poll();
        if (view instanceof AdapterView) {
            setAdapterProxy((AdapterView) view);
        }
        if (view instanceof ViewGroup) {
            ViewGroup group = (ViewGroup) view;
            int count = group.getChildCount();
            for (int i = 0; i < count; i++) {
                views.offer(group.getChildAt(i));
            }
        }
    }
}
 

private void recycleAdapterView(FoldableItemLayout layout) {
    if (layout.getBaseLayout().getChildCount() == 0) {
        return; // Nothing to recycle
    }

    View view = layout.getBaseLayout().getChildAt(0);
    layout.getBaseLayout().removeAllViews();

    Integer type = viewsTypesMap.remove(view);
    if (type != null) {
        Queue<View> cache = recycledViews.get(type);
        if (cache == null) {
            recycledViews.put(type, cache = new LinkedList<>());
        }
        cache.offer(view);
    }
}
 

public static void main(String[] args) {

		Queue<String> q = new PriorityQueue<>();
		q.offer("apple");
		q.offer("pear");
		q.offer("banana");
		System.out.println(q.poll()); // apple
		System.out.println(q.poll()); // banana
		System.out.println(q.poll()); // pear
		System.out.println(q.poll()); // null,因为队列为空

		PriorityQueue<Subject> priorityQueue = new PriorityQueue<Subject>();
		priorityQueue.offer(new Subject(1, 88));
		priorityQueue.offer(new Subject(1, 87));
		priorityQueue.offer(new Subject(1, 90));

		System.out.println(priorityQueue.poll());
		System.out.println(priorityQueue.poll());
		System.out.println(priorityQueue.poll());
	}
 

/**
 * Use one queue and delimiter to print level by level
 */
public void levelByLevelOneQueueUsingDelimiter(Node root) {
    if (root == null) {
        return;
    }
    Queue<Node> q = new LinkedList<Node>();
    q.offer(root);
    q.offer(null);
    while (!q.isEmpty()) {
        root = q.poll();
        if (root != null) {
            System.out.print(root.data + " ");
            if (root.left != null) {
                q.offer(root.left);
            }
            if (root.right != null) {
                q.offer(root.right);
            }
        } else {
            if (!q.isEmpty()) {
                System.out.println();
                q.offer(null);
            }
        }
    }
}
 

/**
 * Start receiving from the next receiveGroup
 * @param receiveGroup the next receiveGroup
 */
public void startGroup(int receiveGroup, int sendGroup,
                       Map<Integer, Integer> expectedReceives) {
  receiveProgressTracker.switchGroup(receiveGroup);
  List<Integer> receiveExecs = receiveGroupsWorkers.get(receiveGroup);
  this.expectedReceivePerWorker = expectedReceives;
  currentReceives.clear();
  for (int i = 0; i < receiveExecs.size(); i++) {
    int exec = receiveExecs.get(i);
    int expected = expectedReceives.get(exec);
    // we offer the buffer only if we are expecting some messages
    if (expected > 0) {
      Queue<DataBuffer> list = receiveBuffers.get(exec);
      // poll the free receive buffers and ad to the receive
      DataBuffer buffer = freeReceiveBuffers.poll();
      if (buffer == null) {
        throw new RuntimeException("Buffer cannot be null");
      }
      list.offer(buffer);
    }
    currentReceives.put(exec, 0);
  }
}
 

public static Node reconByLevelString(String levelStr) {
    String[] values = levelStr.split("_");
    int index = 0;
    Node head = generateNodeByString(values[index++]);
    Queue<Node> queue = new LinkedList<Node>();
    if (head != null) {
        queue.offer(head);
    }
    Node node = null;
    while (!queue.isEmpty()) {
        node = queue.poll();
        node.left = generateNodeByString(values[index++]);
        node.right = generateNodeByString(values[index++]);
        if (node.left != null) {
            queue.offer(node.left);
        }
        if (node.right != null) {
            queue.offer(node.right);
        }
    }
    return head;
}
 

/**
 *
 * @param o the value to buffer
 * @throws MissingBackpressureException
 *             if more onNext are sent than have been requested
 */
public void onNext(Object o) throws MissingBackpressureException {
    boolean iae = false;
    boolean mbe = false;
    synchronized (this) {
        Queue<Object> q = queue;
        if (q != null) {
            mbe = !q.offer(NotificationLite.next(o));
        } else {
            iae = true;
        }
    }

    if (iae) {
        throw new IllegalStateException("This instance has been unsubscribed and the queue is no longer usable.");
    }
    if (mbe) {
        throw new MissingBackpressureException();
    }
}
 

private void recycleView(View view, int index)
{
    Log.v(TAG, "recycleView");
    final int viewType = (Integer) view.getTag(R.id.mediadata_tag_viewtype);
    if (viewType > 0)
    {
        Queue<View> recycledViewsForType = recycledViews.get(viewType);
        if (recycledViewsForType == null)
        {
            recycledViewsForType = new ArrayDeque<View>();
            recycledViews.put(viewType, recycledViewsForType);
        }
        recycledViewsForType.offer(view);
    }
}
 

/**
 * BFS.
 * Generate all possible next strings by removing one paren from current string.
 * First add the original string to a queue and a set to start BFS.
 * While queue is not empty:
 * | Poll a string from the queue.
 * | Check if the polled string is valid, if its valid:
 * |   Set the found flag. We don't need to generate next level.
 * | If found is true:
 * |   Continue to the next string in queue.
 * | If found is false:
 * |   Generate all possible strings for the next level by removing one parentheses.
 * <p>
 * Note that once we found one valid string, we know the minimum number.
 * No need to generate the next possible strings anymore.
 * Use a String set to avoid BFS cycles or duplicate checks.
 */
public List<String> removeInvalidParentheses(String s) {
  if (s == null) { // "" should return [""].
    return Collections.emptyList();
  }
  List<String> res = new ArrayList<>();
  Queue<String> queue = new ArrayDeque<>();
  Set<String> visited = new HashSet<>(); // Store visited strings.
  queue.offer(s);
  visited.add(s);
  boolean found = false; // Flag to stop generating new strings.
  while (!queue.isEmpty()) {
    String cur = queue.poll();
    // Visit.
    if (isValid(cur)) { // First valid string is found.
      res.add(cur);
      found = true;
    }
    if (found) { // No need to generate the more strings.
      continue; // Still check all the strings remain in queue.
    }
    // Generate all possible strings by removing one paren.
    for (int i = 0; i < cur.length(); i++) {
      if (cur.charAt(i) != '(' && cur.charAt(i) != ')') { // Skip chars that are not paren.
        continue;
      }
      cur = cur.substring(0, i) + cur.substring(i + 1); // Remove i.
      if (!visited.contains(cur)) {
        queue.add(cur);
        visited.add(cur);
      }
    }
  }
  return res;
}
 

@Test
public void testParseOptsMultiPutsAndAutoFlushOrder() {
  Queue<String> opts = new LinkedList<>();
  String cmdName = "sequentialWrite";
  String cmdMultiPut = "--multiPut=10";
  String cmdAutoFlush = "--autoFlush=true";
  opts.offer(cmdAutoFlush);
  opts.offer(cmdMultiPut);
  opts.offer(cmdName);
  opts.offer("64");
  PerformanceEvaluation.TestOptions options = null;
  options = PerformanceEvaluation.parseOpts(opts);
  assertNotNull(options);
  assertEquals(true, options.autoFlush);
  assertEquals(10, options.getMultiPut());

  // Change the order of AutoFlush and Multiput
  opts = new LinkedList<>();
  opts.offer(cmdMultiPut);
  opts.offer(cmdAutoFlush);
  opts.offer(cmdName);
  opts.offer("64");

  options = null;
  options = PerformanceEvaluation.parseOpts(opts);
  assertNotNull(options);
  assertEquals(10, options.getMultiPut());
  assertEquals(true, options.autoFlush);
}
 

private static void enqueueAd(final AppLovinAd ad, final String zoneId)
{
    synchronized ( GLOBAL_INTERSTITIAL_ADS_LOCK )
    {
        Queue<AppLovinAd> preloadedAds = GLOBAL_INTERSTITIAL_ADS.get( zoneId );
        if ( preloadedAds == null )
        {
            preloadedAds = new LinkedList<AppLovinAd>();
            GLOBAL_INTERSTITIAL_ADS.put( zoneId, preloadedAds );
        }

        preloadedAds.offer( ad );
    }
}
 

/**
 * TODO Add method documentation
 */
private ReadFuture newReadFuture() {
    Queue<ReadFuture> readyReadFutures = getReadyReadFutures();
    Queue<ReadFuture> waitingReadFutures = getWaitingReadFutures();
    ReadFuture future;
    synchronized (readyReadFutures) {
        future = waitingReadFutures.poll();
        if (future == null) {
            future = new DefaultReadFuture(this);
            readyReadFutures.offer(future);
        }
    }
    return future;
}
 

/**
 * Iterates through policy vocabulary and extracts set of namespaces used in
 * the policy expression.
 *
 * @return collection of used namespaces within given policy instance
 * @throws PolicyException Thrown if internal processing failed.
 */
private Collection<String> getUsedNamespaces() throws PolicyException {
    final Set<String> namespaces = new HashSet<String>();
    namespaces.add(getNamespaceVersion().toString());

    if (this.policyId != null) {
        namespaces.add(PolicyConstants.WSU_NAMESPACE_URI);
    }

    final Queue<ModelNode> nodesToBeProcessed = new LinkedList<ModelNode>();
    nodesToBeProcessed.add(rootNode);

    ModelNode processedNode;
    while ((processedNode = nodesToBeProcessed.poll()) != null) {
        for (ModelNode child : processedNode.getChildren()) {
            if (child.hasChildren()) {
                if (!nodesToBeProcessed.offer(child)) {
                    throw LOGGER.logSevereException(new PolicyException(LocalizationMessages.WSP_0081_UNABLE_TO_INSERT_CHILD(nodesToBeProcessed, child)));
                }
            }

            if (child.isDomainSpecific()) {
                final AssertionData nodeData = child.getNodeData();
                namespaces.add(nodeData.getName().getNamespaceURI());
                if (nodeData.isPrivateAttributeSet()) {
                    namespaces.add(PolicyConstants.SUN_POLICY_NAMESPACE_URI);
                }

                for (Entry<QName, String> attribute : nodeData.getAttributesSet()) {
                    namespaces.add(attribute.getKey().getNamespaceURI());
                }
            }
        }
    }

    return namespaces;
}
 

public void printBinTree(TreeNode root){
    if (root == null) return;

    Queue<TreeNode> queue = new LinkedList<>();
    queue.offer(root);
    int nextLevel = 0;
    int thisLevel = 1;

    while (!queue.isEmpty()){
        TreeNode currNode = queue.poll();

        if (currNode.left != null){
            queue.offer(currNode.left);
            nextLevel ++;
        }

        if (currNode.right != null){
            queue.offer(currNode.right);
            nextLevel ++;
        }


        System.out.print(currNode.val + "\t");
        thisLevel --;

        if (thisLevel == 0){
            System.out.println();
            thisLevel = nextLevel;
            nextLevel = 0;
        }
    }
}
 

private void setDistance(Cell input[][], int x, int y, int distance[][]){
	
	boolean visited[][] = new boolean[input.length][input[0].length];
	Queue<Point> q = new LinkedList<>();
	q.offer(new Point(x,y));
	//Do a BFS at keep updating distance.
	while(!q.isEmpty()){
		Point p = q.poll();
		setDistanceUtil(q, input, p, getNeighbor(input, p.x+1, p.y), distance, visited);
		setDistanceUtil(q, input, p, getNeighbor(input, p.x, p.y+1), distance, visited);
		setDistanceUtil(q, input, p, getNeighbor(input, p.x-1, p.y), distance, visited);
		setDistanceUtil(q, input, p, getNeighbor(input, p.x, p.y-1), distance, visited);
	}
}
 

private void enqFlowInfo(FlowInfo flowInfo) {
    String key = flowInfo.uniqueFlowInfoKey();
    Queue<FlowInfo> queue = flowInfoMap.get(key);
    if (queue == null) {
        Queue<FlowInfo> newQueue = new LinkedList<FlowInfo>();
        newQueue.offer(flowInfo);
        flowInfoMap.put(key, newQueue);
        return;
    }
    queue.offer(flowInfo);

    while (queue.size() > DEFAULT_DATA_POINT_SIZE) {
        queue.remove(); // Removes a garbage data in the queue.
    }
}
 

/**
 * Graph. Topological Sort. BFS.
 * Two steps:
 * 1) Build a graph and in-degree from the given words.
 * 2) Do topological sort.
 * <p>
 * Topological sort based on Kahn's algo.
 * It needs a graph and each node's in-degree.
 * Then start with all 0 in-degree nodes, enqueue them.
 * While the queue is not empty, dequeue a node and add to result order.
 * Remove edges start from this node by reducing the in-degree of its neighbors.
 * If those nodes become 0 in-degree as well, enqueue.
 * When queue is empty, it's done.
 * Before return, check if the order is valid by comparing the result length with # of graph nodes.
 */
public String alienOrder(String[] words) {
  if (words == null || words.length == 0) return "";

  Map<Character, Integer> inDegrees = new HashMap<>();
  for (String s : words) { // Init in-degree of all characters given to 0.
    for (char c : s.toCharArray()) {
      inDegrees.put(c, 0);
    }
  }

  Map<Character, Set<Character>> graph = new HashMap<>(); // Use set to avoid duplicate edge.
  for (int i = 0; i < words.length - 1; i++) {
    String w1 = words[i];
    String w2 = words[i + 1];
    if (w1.startsWith(w2) && w1.length() > w2.length()) { // "abcee" -> "abc", invalid.
      return "";
    }
    for (int j = 0; j < w1.length() && j < w2.length(); j++) {
      char c1 = w1.charAt(j);
      char c2 = w2.charAt(j);
      if (c1 != c2) {
        if (!graph.containsKey(c1)) {
          graph.put(c1, new HashSet<>());
        }
        if (graph.get(c1).add(c2)) {
          inDegrees.put(c2, inDegrees.get(c2) + 1);
        }
        break; // Should break once one edge is found.
      }
    }
  }

  Queue<Character> queue = new ArrayDeque<>();
  for (Map.Entry<Character, Integer> e : inDegrees.entrySet()) {
    if (e.getValue() == 0) queue.offer(e.getKey());
  }
  StringBuilder order = new StringBuilder();
  while (!queue.isEmpty()) {
    char n = queue.poll();
    order.append(n);
    // Remove edges from graph by updating in degrees of neighbors.
    if (graph.containsKey(n)) { // Avoid NPE.
      for (char neighbor : graph.get(n)) {
        inDegrees.put(neighbor, inDegrees.get(neighbor) - 1); // Update in degree.
        if (inDegrees.get(neighbor) == 0) { // Add 0 in degree node to queue.
          queue.offer(neighbor);
        }
      }
    }
  }
  return order.length() == inDegrees.size() ? order.toString() : ""; // Check if all nodes are in result.
}
 

private int generateBreakUpSuggestions(Term term, IndexReader ir,
    int numberBreaks, int maxSuggestions, int useMinSuggestionFrequency,
    SuggestWord[] prefix, Queue<SuggestWordArrayWrapper> suggestions,
    int totalEvaluations, BreakSuggestionSortMethod sortMethod)
    throws IOException {
  String termText = term.text();
  int termLength = termText.codePointCount(0, termText.length());
  int useMinBreakWordLength = minBreakWordLength;
  if (useMinBreakWordLength < 1) {
    useMinBreakWordLength = 1;
  }
  if (termLength < (useMinBreakWordLength * 2)) {
    return 0;
  }    
  
  int thisTimeEvaluations = 0;
  for (int i = useMinBreakWordLength; i <= (termLength - useMinBreakWordLength); i++) {
    int end = termText.offsetByCodePoints(0, i);
    String leftText = termText.substring(0, end);
    String rightText = termText.substring(end);
    SuggestWord leftWord = generateSuggestWord(ir, term.field(), leftText);
    
    if (leftWord.freq >= useMinSuggestionFrequency) {
      SuggestWord rightWord = generateSuggestWord(ir, term.field(), rightText);
      if (rightWord.freq >= useMinSuggestionFrequency) {
        SuggestWordArrayWrapper suggestion = new SuggestWordArrayWrapper(
            newSuggestion(prefix, leftWord, rightWord));
        suggestions.offer(suggestion);
        if (suggestions.size() > maxSuggestions) {
          suggestions.poll();
        }
      }        
      int newNumberBreaks = numberBreaks + 1;
      if (newNumberBreaks <= maxChanges) {
        int evaluations = generateBreakUpSuggestions(new Term(term.field(),
            rightWord.string), ir, newNumberBreaks, maxSuggestions,
            useMinSuggestionFrequency, newPrefix(prefix, leftWord),
            suggestions, totalEvaluations, sortMethod);
        totalEvaluations += evaluations;
      }
    }
    
    thisTimeEvaluations++;
    totalEvaluations++;
    if (totalEvaluations >= maxEvaluations) {
      break;
    }
  }
  return thisTimeEvaluations;
}