collections

问题 I have a Download Queue implemented with BlockingCollection<> . Now I want to prioritize some Download once in a while. I thought it might be great to move some elements 'up' the Collection, like in a list, but there is no method like Remove()/AddFirst() or Move(). What's the preferred way of arranging items in a BlockingCollection<> ? 回答1: BlockingCollection<T> works by wrapping an internal IProducerConsumerCollection<T>. The default is to use a ConcurrentQueue<T> internally, but you can

问题 If i have IEnumberable<Car> list and i want to remove an item from this list based on a property of the car i want something like: list.RemoveWhere(r=>r.Year > 2000) does something like this exist ? i am doing this over and over so i want to avoid copying the list each time to just remove one item 回答1: IEnumberable is immutable, but you can do something like this: list = list.Where(r=>r.Year<=2000) or write an extension method: public static IEnumerable<T> RemoveWhere<T>(this IEnumerable<T>

问题 I have some entries with dates in my database. What is best?: Fetch them with a sql statement and also apply order by . Get the list with sql, and order them within the application with collection.sort or so? Thanks 回答1: To some extent, it depends on how many values are in the complete collection. If it is, say, 20-30 values then you can sort anywhere — even a relatively poor sorting algorithm can do that quickly (avoid Stooge Sort though; that's terrible) — as that is the sort of size of

问题 For all the methods in Collections that take a List as their first argument, why aren't those methods simply part of the List interface? My intuition is: given a List object, that object itself should "know" how to perform on itself operations such as rotate(), shuffle(), or reverse(). But instead, as a Java programmer, I have to review both the methods in the List interface, as well as the static methods "over there" in the Collections class, to ensure I'm using a canonical solution. Why

问题 I am trying Guava for the first time and I find it really awesome. I am executing few parameterized retrieve queries on a Spring jdbc template. The method in the DAO ( AbstractDataAccessObject ) goes like this. No problem here. public Map<String,Object> getResultAsMap(String sql, Map<String,Object> parameters) { try { return jdbcTemplate.queryForMap(sql, parameters); } catch (EmptyResultDataAccessException e) { //Ignore if no data found for this query logger.error(e.getMessage(), e); } return

问题 I'm attempting to load JSON (from php's json_encode) into a Backbone JS collection. I've simplified the problem to: var myJSON = '[{ "id":"1","name":"some name","description":"hmmm"}]'; var myCollection = new MyCollection(myJSON, { view: this }); And: MyObject = Backbone.Model.extend({ id: null, name: null, description: null }); MyCollection = Backbone.Collection.extend({ model: MyObject, initialize: function (models,options) { } }); Error: Uncaught TypeError: Cannot use 'in' operator to

问题 I have committed to learning C now, I'm good with Python/PHP/Bash but I've decided I'm limited by not being fluent in C. However I cannot imagine working in a language without lists and hashes, maybe I'm just jumping a gun, but surely there are 'standard' collection libraries. I do not see any in the GNU standard lib though, any suggestions? 回答1: There is no "standard" set of collection classes for C. Many people simply roll their own as needed. But of course, there are some libraries filling

问题 I know how I can use the Java libraries, and I can write some loops that do the stuff I need for me, but the question is more, why is there nothing in scala.collection.JavaConverters or scala.collection.JavaConverstions to convert a java.util.stream.Stream to a scala.collection.immutable.Stream ? I would like to do something like this: def streamFiles(path: Path): Stream[Path] = { Files.newDirectoryStream(path).asScala } But instead I have to write something like this: def streamFiles(path:

问题 I know how I can use the Java libraries, and I can write some loops that do the stuff I need for me, but the question is more, why is there nothing in scala.collection.JavaConverters or scala.collection.JavaConverstions to convert a java.util.stream.Stream to a scala.collection.immutable.Stream ? I would like to do something like this: def streamFiles(path: Path): Stream[Path] = { Files.newDirectoryStream(path).asScala } But instead I have to write something like this: def streamFiles(path:

问题 I have been refactoring throwaway code which I wrote some years ago in a FORTRAN-like style. Most of the code is now much more organized and readable. However the heart of the algorithm (which is performance-critical) uses 1- and 2-dimensional Java arrays and is typified by: for (int j = 1; j < len[1]+1; j++) { int jj = (cont == BY_TYPE) ? seq[1][j-1] : j-1; for (int i = 1; i < len[0]+1; i++) { matrix[i][j] = matrix[i-1][j] + gap; double m = matrix[i][j-1] + gap; if (m > matrix[i][j]) {