Sollicitatievraag bij Citibank

ConcurrentLinkedHashMap & Its internal working? CompletableFutures? Java 8 features? What is ConcurrentModificationException and when it occurs? Treemap vs HashMap? which one we should prefer if there are less insertion and heavy reads? What is Synchronization and Semaphore? Singleton design pattern and its implementation? how singleton behave in case of multiple thread accessing it? which collection is provide direct access? Ans: ArrayList, Hashmap