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Java collections questions update#

As a result, it mostly serves to store information that is subject to change, including usernames and passwords. What is the Properties file’s major advantage?Īnswer) The key benefit of using a properties file in Java is that any changes to those values are automatically reflected in the Java class without the need to recompile it.Every node contains two links-one that connects to the node after it and another that links to the node before it-which makes this possible. There are no references or pointers to the preceding node stored there.ĭoppelganger lists: Unlike other types of linked lists, doubly linked lists allow traversal of the data items in both directions. Each node in a singly linked list keeps a reference to the node after it in the list, as well as the contents of that node. One-way linked list: Data structures include singly linked lists. Describe how Java supports linked lists.Īnswer) Java supports the following two forms of linked lists:.Unlike the Set interface, which only permits one null value, the List interface supports an unlimited number of null values. The only legacy class in the List interface is the Vector class, while the Set interface lacks any legacy classes. In contrast to the unordered Set collection, which does not retain insertion order, the List is an ordered collection that does. The following list of distinctions between the two, nonetheless, is not exhaustive.Īnswer) While Set has unique objects, List can have duplicate pieces.

The interface for the collection is expanded by the List and Set.

In contrast to collections, where size can be adjusted dynamically as needed, arrays are always of a fixed size, meaning that a user cannot alter the length of an array to meet their needs or at runtime.Ĭollections allow the storage of heterogeneous objects, as contrast to Arrays which may only store objects of the same kind.Ĭollections contain preconfigured methods that can be used for user requirements like sorting, searching, etc. Here are the key distinctions between an array and a collection:

What are the primary distinctions between an array and a collection?Īnswer) Although they have certain similarities when it comes to handling and storing object references, arrays and collections are very different from one another.

For this reason, it offers a variety of classes and interfaces, including ArrayList, Vector, Stack, and HashSet, among others.

What exactly does the Java Collection framework do?Īnswer) To store and modify data in the form of objects, the Collection Framework, a combination of classes and interfaces, is employed.

Also, resizing this or any other kind of hash table is a relatively slow operation, so, when possible, it is a good idea to provide estimates of expected table sizes in constructors.Technical Interview Questions on Java Collections A value of one is appropriate when it is known that only one thread will modify and all others will only read. But overestimates and underestimates within an order of magnitude do not usually have much noticeable impact. Using a significantly higher value than you need can waste space and time, and a significantly lower value can lead to thread contention. Ideally, you should choose a value to accommodate as many threads as will ever concurrently modify the table. Because placement in hash tables is essentially random, the actual concurrency will vary. The table is internally partitioned to try to permit the indicated number of concurrent updates without contention.

Java collections questions update#

The allowed concurrency among update operations is guided by the optional concurrencyLevel constructor argument (default 16), which is used as a hint for internal sizing.

This class is different from Hashtable in terms of locking it means that hashtable use object level lock but this class uses bucket level lock thus having better performance. In this class put and remove methods are synchronized but not get method. Ans) A concurrentHashMap is a thread-safe implementation of Map interface.