What is a HashMap in Java used for?

A HashMap in Java is primarily utilized to store key-value pairs, making it a powerful data structure for managing data that requires fast lookups. The keys in a HashMap are unique identifiers that allow for efficient retrieval of corresponding values. This functionality provides a way to associate data elements with descriptive keys, thereby enhancing data organization and accessibility.

This structure allows for quick access to values by their keys, which is particularly useful in scenarios where performance is critical, and rapid data retrieval is needed. HashMaps work by using a hash function to compute an index into an array of buckets or slots, from which the desired value can be found.

The other options do not accurately describe the primary use of a HashMap in Java. For instance, storing arrays is not the main purpose of a HashMap, as it specifically deals with key-value associations rather than simply holding sequences of data. Performing calculations and displaying graphics also do not align with the functionalities offered by a HashMap. Instead, these tasks may involve other Java classes or libraries designed for mathematical operations or graphical user interfaces.