collections

问题 I am a Java programmer, I have used a Java ArrayList before and now I want to have something like that in C#. Some of options I need are in this Java code: String[] strs = new String[]{"str1" , "str2" , "str3" , "str4"}; ArrayList arrayList = new ArrayList(35); arrayList.add(strs[0]); arrayList.add(strs[1]); arrayList.remove(0); arrayList.set(0, strs[2]); String s = (String) arrayList.get(1); I used C# ArrayList and LinkedList , but they don't have these simple options that I need. Is there

问题 This question already has answers here : es6 Map and Set complexity, v8 implementation (2 answers) Closed 4 years ago . Behind the scenes, in V8, are JavaScript-Map-object's keys indexed in some manner that optimizes the map.get method? Or does map.get() simply just loop through the entire map until it discovers a key match? I'm interested in the efficiency of map.get on larger mappings of 500,000+ key/value pairs. I have this many mappings that I'd like to just cache in RAM, instead of

问题 Basically I look for a way to avoid working with entry -> entry.getValue and entry -> entry.getKey similar to what Map.forEach() does. If only I could get a way to work as map.stream().filter((k,v) -> ) ... and so on It seems the interface is called BiConsumer. Perhaps with a converter to BiConsumer or a Stream.generate() someway 回答1: Since this is a repeating question, I will throw a full solution into the ring. It’s a PairStream type that is by default a simple wrapper around an ordinary

问题 I can't seem to figure this one out by reading the documentation for ObservableCollection.Move(int oldIndex, int newIndex) on MSDN: oldIndex Type: System.Int32 The zero-based index specifying the location of the item to be moved. newIndex Type: System.Int32 The zero-based index specifying the new location of the item. I don't understand how it works. What happens to the item with newIndex ? My assumption is that the index of each item with index >= newIndex is decremented. Is that assumption

问题 I want to select the list of all orders in Magento. This is required for me to show the list of all the orders from magento in another PHP application presently I'm working on. Also can some one write me the code using the Magento conventions such as Mage:: Im using Magento 1.4.2 version. Thanks, Mark 回答1: This code uses the "Magento way" and accesses the data through the Model layer which insulates you from changes in the table structure (e.g. flat vs EAV). Create a new PHP file containing

问题 I have a collection of objects that I would like to partition into two collections, one of which passes a predicate and one of which fails a predicate. I was hoping there would be a Guava method to do this, but the closest they come is filter, which doesn't give me the other collection. I would image the signature of the method would be something like this: public static <E> Pair<Collection<E>, Collection<E>> partition(Collection<E> source, Predicate<? super E> predicate) I realize this is

问题 I would like to merge two Map with JAVA 8 Stream: Map<String, List<String>> mapGlobal = new HashMap<String, List<String>>(); Map<String, List<String>> mapAdded = new HashMap<String, List<String>>(); I try to use this implementation: mapGlobal = Stream.of(mapGlobal, mapAdded) .flatMap(m -> m.entrySet().stream()) .collect(Collectors.groupingBy(Map.Entry::getKey, Collectors.mapping(Map.Entry::getValue, Collectors.toList()) )); However, this implementation only create a result like: Map<String,

问题 I want to make a ComboBox filled with all the colors from System.Drawing.Color But I can't seem to collect all the colors from that collection I've already tried using a foreach to do the job like this: foreach (Color clr in Color) { } But all I get is an error. So how can I loop trough all the colors? Any help will be appreciated. 回答1: You could take color from KnownColor KnownColor[] colors = Enum.GetValues(typeof(KnownColor)); foreach(KnownColor knowColor in colors) { Color color = Color

问题 I have this: Post.paragraphs << new_paragraph And I need to remove paragraph by id = 3, so the following deletes the record completely: Post.paragraphs.find(paragraph_id).destroy # or Post.paragraphs.find(paragraph_id).delete I just need to remove a paragraph from has_many association. I tried to use delete and destroy . Both methods completely delete records from the associated tables. How can I just remove them from the "container"? 回答1: You should not use the delete method on the Paragraph

问题 This is a pretty common question, but I could not find this part: Say I have this array list: List<MyDataClass> arrayList = new List<MyDataClass>; MyDataClass{ String name; String age; } Now, I need to find duplicates on the basis of age in MyDataClass and remove them. How is it possible using something like HashSet as described here? I guess, we will need to overwrite equals in MyDataClass? But, what if I do not have the luxury of doing that? And How does HashSet actually internally find and