Union or intersection of Java Sets
The simplest one-line solution is this: The above solution is destructive, meaning that contents of the original set1 my change.If you don’t want to touch your existing sets, create a new set:
collections
How to sort a HashSet?
For lists, we use the Collections.sort(List) method. What if we want to sort a HashSet?
Why is a ConcurrentModificationException thrown and how to debug it
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. This will throw a ConcurrentModificationException when the it.hasNext() is called the second time. The correct approach would be Assuming this iterator supports the remove() operation.
Most efficient way to increment a Map value in Java
Some test results I’ve gotten a lot of good answers to this question–thanks folks–so I decided to run some tests and figure out which method is actually fastest. The five methods I tested are these: the “ContainsKey” method that I presented in the question the “TestForNull” method suggested by Aleksandar Dimitrov the “AtomicLong” method suggested … Read more
Thread-safe List property
If you are targetting .Net 4 there are a few options in System.Collections.Concurrent Namespace You could use ConcurrentBag<T> in this case instead of List<T>
MongoDB Show all contents from all collections
Once you are in terminal/command line, access the database/collection you want to use as follows: choose your collection and type the following to see all contents of that collection: More info here on the MongoDB Quick Reference Guide.
Any implementation of Ordered Set in Java?
Take a look at LinkedHashSet class From Java doc: Hash table and linked list implementation of the Set interface, with predictable iteration order. This implementation differs from HashSet in that it maintains a doubly-linked list running through all of its entries. This linked list defines the iteration ordering, which is the order in which elements were inserted into the … Read more
HashSet vs. List performance
A lot of people are saying that once you get to the size where speed is actually a concern that HashSet<T> will always beat List<T>, but that depends on what you are doing. Let’s say you have a List<T> that will only ever have on average 5 items in it. Over a large number of cycles, if a single item … Read more
Any implementation of Ordered Set in Java?
Take a look at LinkedHashSet class From Java doc: Hash table and linked list implementation of the Set interface, with predictable iteration order. This implementation differs from HashSet in that it maintains a doubly-linked list running through all of its entries. This linked list defines the iteration ordering, which is the order in which elements were inserted into the … Read more
How to easily initialize a list of Tuples?
c# 7.0 lets you do this: If you don’t need a List, but just an array, you can do: And if you don’t like “Item1” and “Item2”, you can do: or for an array: which lets you do: tupleList[0].Index and tupleList[0].Name Framework 4.6.2 and below You must install System.ValueTuple from the Nuget Package Manager. Framework 4.7 and above It is built … Read more