Which of the following is a terminal operation in the Stream API?

The reduce() method is a terminal operation in the Stream API that reduces the elements of a stream into a single result using a given accumulator function. This method is particularly useful for performing aggregate operations, such as summing a list of numbers, finding the maximum or minimum value, or concatenating strings. The reduce() method takes two arguments: an initial value (or identity) and a binary operator, which defines how the elements are combined.

Terminal operations in the Stream API, like reduce(), are crucial because they trigger the execution of the entire stream pipeline. Until a terminal operation is invoked, the intermediate operations in a stream pipeline are not executed, as streams are lazy by nature. This laziness allows for performance optimizations, as the operations are only performed when necessary. Once the terminal operation is called, the stream is consumed, and the final result is produced.

Other examples of terminal operations in the Stream API include collect(), forEach(), and count(). These operations mark the end of the stream pipeline and produce a final result or side effect. The reduce() method is particularly powerful in scenarios where a single value needs to be derived from a collection of elements, making it a key tool in functional programming with Java.