it1 = coll1.iterator(); it2 = coll2.iterator(); while(it1.hasNext() && it2.hasNext()) { value1 = it1.next(); value2 = it2.next(); do something with it1 and it2; } This version terminates when the shorter collection is exhausted; alternatively, you could continue until the longer one is exhausted, setting value1 resp. value2 to null.
Assuming you’re using .NET 3.5: dic.Keys.First(); Note that there’s no guaranteed order in which key/value pairs will be iterated over in a dictionary. You may well find that in lots of cases you get out the first key that you put into the dictionaries – but you absolutely must not rely on that. As Skirwan … Read more
A Collection is not a necessarily ordered set of elements so there may not be a concept of the “last” element. If you want something that’s ordered, you can use a SortedSet/NavigableSet which has a last() method. Or you can use a List and call mylist.get(mylist.size()-1); If you really need the last element you should … Read more
Each index will basically be a separate Map. You can (and probably should) abstract this behind a class that manages the searches, indexing, updates and removals for you. It wouldn’t be hard to do this fairly generically. But no, there’s no standard out of the box class for this although it can easily be built … Read more
Some types of collections can add cheaply to the front (lists, seqs), while others can add cheaply to the back (vectors, queues, kinda-sorta lazy-seqs). Rather than using concat, if possible you should arrange to be working with one of those types (vector is most common) and just conj to it: (conj [1 2 3] 4) … Read more
Assuming you’re using .NET 3.5 or later (using System.Linq;): string[] keys = dictionary.Keys.ToArray(); Otherwise, you will have to use the CopyTo method, or use a loop : string[] keys = new string[dictionary.Keys.Count]; dictionary.Keys.CopyTo(keys, 0);
Try the following var equal = expected.SequenceEqual(actual); Test Version Assert.IsTrue( actual.SequenceEqual(expected) ); The SequenceEqual extension method will compare the elements of the collection in order for equality. See http://msdn.microsoft.com/en-us/library/bb348567(v=vs.100).aspx
In your case, there’s no need to iterate through the list, because you know which object to delete. You have several options. First you can remove the object by index (so if you know, that the object is the second list element): a.remove(1); // indexes are zero-based Or, you can remove the first occurence of … Read more
Collections.emptyList() does not need to create a new object for each call; it’s typical, as in OpenJDK, to just return the singleton EMPTY_LIST object. Additionally, it’s clearer that you intend to mean an empty list rather than having forgotten to fill in a placeholder. Use emptyList(); it’s both faster (up to Java target level 1.9) … Read more
Why: As described before, the problem is that Dictionary requires an implementation of the Object.GetHashCode() method. null does not have an implementation, therefore no hash code associated. Solution: I have used a solution similar to a NullObject pattern using generics that enables you to use the dictionary seamlessly (no need for a different dictionary implementation). … Read more