TL;DR: assuming your deque is called d, just inspect d[0], since the “leftmost” element in a deque is the front (you might want to test before the length of the deque to make sure it’s not empty). Taking @asongtoruin’s suggestion, use if d: to test whether the deque is empty (it’s equivalent to if len(d) … Read more
for (Map.Entry<String, ArrayList<String>> entry : test1.entrySet()) { String key = entry.getKey(); ArrayList<String> value = entry.getValue(); // now work with key and value… } By the way, you should really declare your variables as the interface type instead, such as Map<String, List<String>>.
It is pretty obvious that array[10] is faster than array.get(10), as the later internally does the same call, but adds the overhead for the function call plus additional checks. Modern JITs however will optimize this to a degree, that you rarely have to worry about this, unless you have a very performance critical application and … Read more
Try: var dict = Enum.GetValues(typeof(fooEnumType)) .Cast<fooEnumType>() .ToDictionary(t => (int)t, t => t.ToString() );
Specialization has a high cost on the size of classes, so it must be added with careful consideration. In the particular case of collections, I imagine the impact will be huge. Still, it is an on-going effort — Scala library has barely started to be specialized.
The reason is simple: a variable arity parameter is simply an old-school array paramater with some additional metadata that tells the compiler to provide some syntactic sugar (namely, it allows implicit array creation). So from the perspective of the JVM Object… is pretty much the same as Object[]. Allowing collections as well would require a … Read more
The Exception is straightforward and says : Illegal attempt to map a non collection as a @OneToMany, @ManyToMany or @CollectionOfElements, so the cause is obvious here and if we take a look at the Hibernate Collection mapping documentation it clearly states that: As a requirement persistent collection-valued fields must be declared as an interface type … Read more
From the JEP docs itself – Description – These will include varargs overloads, so that there is no fixed limit on the collection size. However, the collection instances so created may be tuned for smaller sizes. Special-case APIs (fixed-argument overloads) for up to ten of elements will be provided. While this introduces some clutter in … Read more
Well, there really aren’t too many options. Let me go through the listed subclasses: DelayQueue, LinkedBlockingDeque, PriorityBlockingQueue, and SynchronousQueue are all made for special cases requiring extra functionality; they don’t make sense in this scenario. That leaves only ArrayBlockingQueue and LinkedBlockingQueue. If you know how to tell whether you need an ArrayList or a LinkedList, … Read more
The argument to defaultdict is a function (or rather, a callable object) that returns the default value. So you can pass in a lambda that returns your desired default. >>> from collections import defaultdict >>> d = defaultdict(lambda: ‘My default’) >>> d[‘junk’] ‘My default’ Edited to explain lambda: lambda is just a shorthand for defining … Read more