What are Stream API used for? What advantages did they add?

Stream API in Java was introduced for convenient and efficient processing of collections and other data sources in a functional style.

Advantages of Stream API:

• Code readability: operations on data are expressed declaratively (e.g., filtering, mapping, sorting).
• Lazy processing: computations are performed only when necessary, which improves performance.
• Parallelism: easily switch to parallel processing using parallelStream(), simplifying multithreading usage.
• Operation composition: you can apply a chain of operations sequentially without modifying the original data.

Example of using Stream API:

List<String> names = Arrays.asList("Anna", "Bob", "Charlie", "David");

List<String> filtered = names.stream()
    .filter(name -> name.startsWith("A"))
    .map(String::toUpperCase)
    .collect(Collectors.toList());

System.out.println(filtered); // [ANNA]

Thus, Stream API makes code more expressive and simplifies data handling.