collections

问题 More specifically I want an interface to compare objects which can be only compared for equality [e.g. complex numbers] but don't have total order on them. It should have [Note that it only returns a boolean yes/no] boolean Equals(T object1, T object2); and a hashcode function. So that when I distribute them into buckets using objects say to collect "equal" objects, 2 "equal" objects don't end up in two different buckets. int getHashCode(T object); Does Java have one? I searched and couldn't

问题 I'm getting an exception whenever I fetch like this Feature f = o.Features.SingleOrDefault(e => e.LinkName == PageLink); because this can return one or more than one element. What is the alternative approach that I can use to solve this issue? 回答1: Single and SingleOrDefault are designed to throw if more that one match exists in the sequence. A consequence of this is that the entire sequence must be iterated prior to completion. It does not sound like this is what you want. Try FirstOrDefault

问题 I'm getting an exception whenever I fetch like this Feature f = o.Features.SingleOrDefault(e => e.LinkName == PageLink); because this can return one or more than one element. What is the alternative approach that I can use to solve this issue? 回答1: Single and SingleOrDefault are designed to throw if more that one match exists in the sequence. A consequence of this is that the entire sequence must be iterated prior to completion. It does not sound like this is what you want. Try FirstOrDefault

问题 Following is my code used to sort a list with predefined order. Defined order is mentioned in itemsSorted list. final List<String> itemsSorted = myMethod.getSortedItems(); List<String> plainItemList = myMethod2.getAllItems(); final Comparator<String> comparator = new Comparator<String>() { public int compare(String str1, String str2) { return orderOf(str1) - orderOf(str2); } private int orderOf(String name) { return ((itemsSorted)).indexOf(name); } }; Collections.sort(plainItemList,

问题 i am filtering data using collections. But i need to use like method. I had tried to write like this : ('name', 'LIKE', '%value%') but it did not work. Here is my method : protected function filterData(Collection $collection, $transformer) { foreach (request()->query() as $query => $value) { $attribute = $transformer::originalAttribute($query); if (isset($attribute, $value)) { $collection = $collection->where($attribute, $value); } } return $collection; } 回答1: The 1st question is whether you

问题 I was trying to loop through a collection based on the key What I am trying to accomplish here is to group each company based on the alphabet in my view. How do I loop through this?? $results = $companies->sortBy('name')->groupBy(function ($item, $key) { return substr($item['name'], 0, 1); }); dump($results); Controller 回答1: As an alternative to @msonowal's answer you can also use each(): $results->each(function ($collection, $alphabet) { dump($alphabet, $collection); }); However, if you're

问题 I was trying to loop through a collection based on the key What I am trying to accomplish here is to group each company based on the alphabet in my view. How do I loop through this?? $results = $companies->sortBy('name')->groupBy(function ($item, $key) { return substr($item['name'], 0, 1); }); dump($results); Controller 回答1: As an alternative to @msonowal's answer you can also use each(): $results->each(function ($collection, $alphabet) { dump($alphabet, $collection); }); However, if you're

问题 I'm currently using a Hashtable wrapped as a Hashtable.Synchronized as a simple cache in a library that could be used by a multi-threaded environment (such as asp.net) - is this a suitable use for this collection? I understand that there are more suitable constructs available in .Net 4.0, but I'm stuck with .Net 3.5. If it makes any difference, this cache is read from frequently, and is written to very infrequently (but needs to remain threadsafe). Basic usage is something along the lines of:

问题 I have ListView which I am binding to a Dictionary collection, but new new items are added to the collection, the listview is not updating. How this can be achieved in WPF? 回答1: Both sides of WPF binding should support INotifyCollectionChanged interface in order to notify about collection changes. Dictionary does not support it. So you can either use ObservableCollection class (it does not provide functionality like search a value by associated key), or you can create you own

问题 This question already has an answer here : How to check a certain data already exists in firestore or not (1 answer) Closed 2 years ago . I want to see what is the error in this code for the executiom, when i compile it it just returns the values of log 1,3,2 , and i wanto log 2 to be before the 3 Log.d("1", "antes de validar"); DocumentReference docRef = db.getDb().collection("Usuarios").document(Correo); docRef.get().addOnCompleteListener(new OnCompleteListener<DocumentSnapshot>() {