Creating a truly compile-time generated constant dictionary in C# is not really a straightforward task. Actually, none of the answers here really achieve that. There is one solution though which meets your requirements, although not necessarily a nice one; remember that according to the C# specification, switch-case tables are compiled to constant hash jump tables. … Read more
An ordered collection means that the elements of the collection have a specific order. The order is independent of the value. A List is an example. A sorted collection means that not only does the collection have order, but the order depends on the value of the element. A SortedSet is an example. In contrast, … Read more
Elements in a weak hashmap can be reclaimed by the garbage collector if there are no other strong references to the key object, this makes them useful for caches/lookup storage. Weak reference are not restricted to these hash tables, you can use WeakReference for single objects. They are useful to save resource, you can keep … Read more
Well there’s always assertThat(list.isEmpty(), is(false)); … but I’m guessing that’s not quite what you meant 🙂 Alternatively: assertThat((Collection)list, is(not(empty()))); empty() is a static in the Matchers class. Note the need to cast the list to Collection, thanks to Hamcrest 1.2’s wonky generics. The following imports can be used with hamcrest 1.3 import static org.hamcrest.Matchers.empty; import … Read more
In the most general case, consider System.Collections.Generic.HashSet as your default “Contains” workhorse data structure, because it takes constant time to evaluate Contains. The actual answer to “What is the fastest searchable collection” depends on your specific data size, ordered-ness, cost-of-hashing, and search frequency.
It is, in my personal experience admittedly, very useful in cases where an API requires a collection of parameters, but you have nothing to provide. For example you may have an API that looks something like this, and does not allow null references: public ResultSet executeQuery(String query, Map<String, Object> queryParameters); If you have a query … Read more
You can index Dictionary, you didn’t need ‘get’. Dictionary<string,string> example = new Dictionary<string,string>(); … example.Add(“hello”,”world”); … Console.Writeline(example[“hello”]); An efficient way to test/get values is TryGetValue (thanx to Earwicker): if (otherExample.TryGetValue(“key”, out value)) { otherExample[“key”] = value + 1; } With this method you can fast and exception-less get values (if present). Resources: Dictionary-Keys Try Get … Read more
From the Java Collections API Design FAQ: Why doesn’t Map extend Collection? This was by design. We feel that mappings are not collections and collections are not mappings. Thus, it makes little sense for Map to extend the Collection interface (or vice versa). If a Map is a Collection, what are the elements? The only … Read more
This is not a synchronization problem. This will occur if the underlying collection that is being iterated over is modified by anything other than the Iterator itself. Iterator it = map.entrySet().iterator(); while (it.hasNext()) { Entry item = it.next(); map.remove(item.getKey()); } This will throw a ConcurrentModificationException when the it.hasNext() is called the second time. The correct … Read more
Or you could just do it that way: public String controllerMethod(@RequestParam(value=”myParam[]”) String[] myParams){ …. } That works for example for forms like this: <input type=”checkbox” name=”myParam[]” value=”myVal1″ /> <input type=”checkbox” name=”myParam[]” value=”myVal2″ /> This is the simplest solution 🙂