java.util.ArrayDeque#getFirst ( )源码实例Demo

public void writeStartElement(final String localName) throws XMLStreamException {
    ArrayDeque<String> namespaces = unspecifiedNamespaces;
    String namespace = namespaces.getFirst();
    if (namespace != NO_NAMESPACE) {
        writeStartElement(namespace, localName);
        return;
    }

    unspecifiedNamespaces.push(namespace);

    // If this is a nested element flush the outer
    nl();
    indent();
    delegate.writeStartElement(localName);

    level++;
    state = START_ELEMENT;
    indentEndElement = false;
}
 

public int[] maxSlidingWindow(int[] nums, int k) {
    int len = nums.length;
    if (len == 0) {
        return new int[0];
    }
    int[] res = new int[len - k + 1];
    ArrayDeque<Integer> queue = new ArrayDeque<>(len);
    for (int i = 0; i < len; i++) {
        // 左边界滑出
        if (i >= k && queue.getFirst() == i - k) {
            queue.removeFirst();
        }

        // 在 nums[i] 加入之前考虑把不可能的值弹出
        while (!queue.isEmpty() && nums[queue.getLast()] <= nums[i]) {
            queue.removeLast();
        }

        queue.add(i);
        // 记录结果
        if (i >= k - 1) {
            res[i - k + 1] = nums[queue.getFirst()];
        }
    }
    return res;
}
 

public int[] maxSlidingWindow(int[] nums, int k) {
    int len = nums.length;
    // 特判
    if (len == 0) {
        return new int[]{};
    }
    // 结果集
    List<Integer> res = new ArrayList<>();
    // 滑动窗口，注意：保存的是索引值
    ArrayDeque<Integer> deque = new ArrayDeque<>(k);

    for (int i = 0; i < len; i++) {
        // 当元素从左边界滑出的时候，如果它恰恰好是滑动窗口的最大值
        // 那么将它弹出
        if (i >= k && i - k == deque.getFirst()) {
            deque.pollFirst();
        }

        // 如果滑动窗口非空，新进来的数比队列里已经存在的数还要大
        // 则说明已经存在数一定不会是滑动窗口的最大值（它们毫无出头之日）
        // 将它们弹出
        while (!deque.isEmpty() && nums[deque.peekLast()] <= nums[i]) {
            deque.pollLast();
        }
        deque.add(i);
        // 队首一定是滑动窗口的最大值的索引
        if (i >= k - 1) {
            res.add(nums[deque.peekFirst()]);
        }
    }

    int size = res.size();
    int[] result = new int[size];

    for (int i = 0; i < size; i++) {
        result[i] = res.get(i);
    }
    return result;
}
 

/**
 * getFirst() returns first element, or throws NSEE if empty
 */
public void testFirstElement() {
    ArrayDeque 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) {}
}
 

/**
 * getFirst() returns first element, or throws NSEE if empty
 */
public void testFirstElement() {
    ArrayDeque 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) {}
}
 

@Override
public void writeStartElement(final String localName) throws XMLStreamException {
    ArrayDeque<String> namespaces = unspecifiedNamespaces;
    String namespace = namespaces.getFirst();
    if (namespace == null ? NO_NAMESPACE != null : ! namespace.equals(NO_NAMESPACE)) {
        writeStartElement(namespace, localName);
        return;
    }

    unspecifiedNamespaces.push(namespace);

    // If this is a nested element flush the outer
    runAttrQueue();
    nl();
    indent();
    attrQueue.add(new ArgRunnable() {
        public void run(int arg) throws XMLStreamException {
            if (arg == 0) {
                delegate.writeStartElement(localName);
            } else {
                delegate.writeEmptyElement(localName);
            }
        }
    });

    level++;
    state = START_ELEMENT;
    indentEndElement = false;
}
 

private String nestUnspecifiedNamespace() {
    ArrayDeque<String> namespaces = unspecifiedNamespaces;
    String clone = namespaces.getFirst();
    namespaces.push(clone);
    return clone;
}
 

@Override
public ExplorerElement create(PresentationEnvironment env) {
	MetaResource rootResource = (MetaResource) env.getElement();
	MetaResource nestedResource = rootResource;

	ArrayDeque<MetaAttribute> attributePath = env.getAttributePath();
	PreconditionUtil.verify(attributePath == null || attributePath.size() < 2, "only relationships supported");
	MetaAttribute relationshipAttribute = attributePath != null ? attributePath.getFirst() : null;
	if (relationshipAttribute != null) {
		nestedResource = (MetaResource) relationshipAttribute.getType().getElementType();
	}

	PresentationService service = env.getService();

	DataTableElement table = createTable(env, nestedResource);

	ExplorerElement explorerElement = new ExplorerElement();
	explorerElement.setId(toId(service, nestedResource));
	explorerElement.setComponentId("explorer");
	explorerElement.setTable(table);
	explorerElement.addAction(createRefreshAction());
	if (rootResource != nestedResource) {
		explorerElement.setPath(StringUtils.nullToEmpty(service.getPath()) + rootResource.getResourcePath() + "/" + relationshipAttribute.getName());

		// no need to show parent again when nested
		MetaAttribute oppositeAttribute = relationshipAttribute.getOppositeAttribute();
		if (oppositeAttribute != null) {
			TableColumnElement oppositeColumn = table.getColumns().getElements().get(oppositeAttribute.getName());
			if (oppositeColumn != null) {
				table.getColumns().remove(oppositeColumn);
			}
		}
	}
	else {
		explorerElement.setPath(service.getPath() + rootResource.getResourcePath());
	}
	explorerElement.setServiceName(service.getServiceName());
	explorerElement.setServicePath(service.getPath());
	explorerElement.setFullTextSearchPaths(getSearchPaths(nestedResource));

	if (nestedResource.isInsertable()) {
		explorerElement.addAction(createPostAction());
	}

	QueryElement query = explorerElement.getBaseQuery();
	query.setResourceType(nestedResource.getResourceType());
	query.setInclusions(PresentationBuilderUtils.computeIncludes(explorerElement.getTable().getChildren()));
	return explorerElement;
}
 

private String nestUnspecifiedNamespace() {
    ArrayDeque<String> namespaces = unspecifiedNamespaces;
    String clone = namespaces.getFirst();
    namespaces.push(clone);
    return clone;
}