
But above all, it is also available for various UI frameworks, including React, Angular, Vue.js, native Android, and iOS applications. Apollo enjoys a good reputation within the GraphQL community and is probably the most widely used client framework for GraphQL applications. The Apollo Client, which is available as open source software, is such a framework that supports this kind of development. A component then no longer states imperatively how the data is fetched, but only which data is required. This is especially useful in times of declarative UI libraries such as React, because it is also possible to declaratively describe data requirements besides the UI. However, there are also frameworks that can support developers in using GraphQL. Theoretically, it would be possible of course to manually send the queries and in turn to manually prepare the result data for the display. There are several options to actually use GraphQL in a client application. A JSON structure, which corresponds exactly with this query, is the response. We are thereby able to query for the exact data, which is currently required, in a single request.

The query also contains the authors and comments for each article. All articles in the listing are queried, but not all of their field are included – only their id and title. Listing 1 shows an example of a request, as it might occur in a blogging application, with blog articles, authors, and comments. The schema is statically typed, which means that the schema’s developers specify types, which describe what kind of data is offered, and how these correlate to each other. Clients can send queries to this schema and receive the corresponding data from the server. Unlike REST, GraphQL does not focus on individual resources with their respective URLs, but on a single GraphQL schema, which is offered by the server. We can achieve this by using the static method (): PriorityQueue reversedQueue = new PriorityQueue(Collections.reverseOrder()) ĪssertThat(reversedQueue.poll()).isEqualTo(3) ĪssertThat(reversedQueue.poll()).isEqualTo(2) ĪssertThat(reversedQueue.poll()).isEqualTo(1) 4.GraphQL is a query language, which allows data to be queried in a JSON-like form from a GraphQL interface. Let’s now create a PriorityQueue sorted in the inverse natural order. isEqualTo(integerQueueWithComparator.poll()) PriorityQueue integerQueueWithComparator = new PriorityQueue((Integer c1, Integer c2) -> pare(c1, c2)) That's because initializing a priority queue with a null Comparator will directly order elements using the compare operation.Īs an example, let’s now see that by providing a standard Integer natural ordering comparator or null, the queue will be ordered in the same way: PriorityQueue integerQueue = new PriorityQueue() In a previous article, we presented how elements inserted into the PriorityQueue are ordered based on their natural ordering. It is instead granted linear time for the remove(Object) and contains(Object) methods and constant time for the retrieval methods ( peek, element, and size). This can happen thanks to the Balanced Binary Heap data structure that is constantly maintained for every edit to the Queue. In the Javadoc, it’s specified that this implementation takes O(log(n)) time for the enqueuing and dequeuing methods ( offer, poll, remove and add). While it’s not mandatory to give an initial capacity to a PriorityQueue, if we already know the size of our collection, it's possible to avoid automatic resizes, which consume CPU cycles that we'd be better off saving. This array is automatically resized if the initial specified capacity (11 by default in JDK 17) is not enough to store all the items. Internally, the PriorityQueue relies on an array of objects. Every retrieval operation of the queue ( poll, remove, or peek) reads the head of the queue. As we may infer from its name, we use PriorityQueue to maintain a defined ordering in a given collection: the first element ( head) of the queue is the most minor element with respect to the ordering we specify. The class was provided starting from the JDK 1.5, which also contains other implementations of the AbstractQueue.
