Actually, probably the “best” way to initialize the ArrayList is the method you wrote, as it does not need to create a new List in any way: The catch is that there is quite a bit of typing required to refer to that list instance. There are alternatives, such as making an anonymous inner class … Read more
First, let’s see what this does:Arrays.asList(ia) It takes an array ia and creates a wrapper that implements List<Integer>, which makes the original array available as a list. Nothing is copied and all, only a single wrapper object is created. Operations on the list wrapper are propagated to the original array. This means that if you shuffle the list … Read more
Summary ArrayList with ArrayDeque are preferable in many more use-cases than LinkedList. If you’re not sure — just start with ArrayList. TLDR, in ArrayList accessing an element takes constant time [O(1)] and adding an element takes O(n) time [worst case]. In LinkedList adding an element takes O(n) time and accessing also takes O(n) time but LinkedList … Read more
Use this method Collections.sort(List,Comparator) . Implement a Comparator and pass it to Collections.sort(). Then use the Comparator as
There are several differences between HashMap and Hashtable in Java: Hashtable is synchronized, whereas HashMap is not. This makes HashMap better for non-threaded applications, as unsynchronized Objects typically perform better than synchronized ones. Hashtable does not allow null keys or values. HashMap allows one null key and any number of null values. One of HashMap’s subclasses is LinkedHashMap, so in the event that you’d want predictable iteration order (which is insertion order by default), you … Read more