What does the method map() do in Java's Stream API?

• A. Filters elements based on a condition
• B. Transforms objects by applying a function
• C. Converts collections to arrays
• D. Sorts elements in a stream

Answer: (B)

The method map() in Java's Stream API is used to transform elements in a stream by applying a specified function to each element. When you invoke map(), it takes a function as an argument and applies that function to each element in the stream, resulting in a new stream of transformed elements. For example, if you have a stream of integers and you want to create a new stream of their squares, you would use the map() method to apply a function that squares each integer.

This method is pivotal in the functional programming paradigm that Java's Stream API embraces, allowing for concise and readable data transformations. The end result is a stream of the same size, but the content is altered according to the transformation defined by the provided function. This capability makes map() a powerful tool in data manipulation and processing tasks where converting data formats or representations is required.