What are the differences between using streams and traditional loops when processing collections?

Streams in Java are an abstraction for processing collections and other sequences of data using a functional style.

Differences from traditional loops:

• Declarative: streams describe what needs to be done, not how. Loops are imperative — they describe a step-by-step process.
• Lazy: operations on streams (e.g., filtering, mapping) are not executed immediately, but only upon a terminal operation.
• Parallelism: streams can easily switch to parallel mode (parallelStream()), simplifying multithreaded processing.
• Readability and conciseness: code with streams is often shorter and more understandable.

Example with a loop:

List<String> names = Arrays.asList("Anna", "Bob", "Charlie");
List<String> filtered = new ArrayList<>();
for (String name : names) {
    if (name.startsWith("A")) {
        filtered.add(name.toUpperCase());
    }
}

Equivalent with streams:

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

Thus, streams simplify and make collection processing more expressive.