You need to store elements in a collection that guarantees that no duplicates are stored and all elements can be accessed in natural order. Which interface provides that capability?a)java.util.Mapb)java.util.Setc)java.util.Listd)java.util.CollectionCorrect answer is option 'B'. Can you explain this answer?

Question

Answer

Understanding the Requirement
To store elements without duplicates and in natural order, the right data structure is crucial. Let's analyze the options available.
Option A: java.util.Map
- A Map stores key-value pairs, where each key is unique.
- However, it doesn't enforce any order on the keys and is not suitable for simple collections of elements.
Option B: java.util.Set
- A Set is specifically designed to hold unique elements.
- It automatically prevents duplicates and offers a natural ordering if implemented via a specific class like TreeSet.
- This makes it the ideal choice for this requirement.
Option C: java.util.List
- A List allows for duplicate elements and maintains the order of insertion.
- While it does provide access in a natural order, it does not meet the uniqueness requirement.
Option D: java.util.Collection
- Collection is a broader interface that encompasses other collections like List, Set, and Queue.
- It does not specify behavior regarding duplicates or ordering.
Conclusion
The best option for storing elements without duplicates while ensuring they can be accessed in natural order is option B: java.util.Set. This structure guarantees uniqueness and, when using implementations like TreeSet, maintains the elements in their natural order.

Answer

Option B is correct. A set is a collection that contains no duplicate elements. The iterator returns the elements in no particular order (unless this set is an instance of some class that provides a guarantee). A map cannot contain duplicate keys but it may contain duplicate values. List and Collection allow duplicate elements.
Option A is wrong. A map is an object that maps keys to values. A map cannot contain duplicate keys; each key can map to at most one value. The Map interface provides three collection views, which allow a map's contents to be viewed as a set of keys, collection of values, or set of key-value mappings. The order of a map is defined as the order in which the iterators on the map's collection views return their elements. Some map implementations, like the TreeMap class, make specific guarantees as to their order (ascending key order); others, like the HashMap class, do not (does not guarantee that the order will remain constant over time).
Option C is wrong. A list is an ordered collection (also known as a sequence). The user of this interface has precise control over where in the list each element is inserted. The user can access elements by their integer index (position in the list), and search for elements in the list. Unlike sets, lists typically allow duplicate elements.
Option D is wrong. A collection is also known as a sequence. The user of this interface has precise control over where in the list each element is inserted. The user can access elements by their integer index (position in the list), and search for elements in the list. Unlike sets, lists typically allow duplicate elements.

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