Why are streams used in the new version of Java?

Streams in Java, introduced in Java 8, provide a new, functional way to work with data collections. Their main advantages are:

• Declarative style: Code becomes more readable and understandable, as we describe what needs to be done with the data, rather than how to do it.
• Parallel execution: Streams are easily parallelizable, allowing efficient use of multi-core processors and increasing performance when processing large volumes of data.
• Lazy operations: Operations on streams are performed only when the result is truly needed. This saves resources and can be useful when working with infinite or very large data streams.
• Improved readability and maintainability: Using chains of operations makes the code more compact and understandable compared to traditional loops.

Example: Converting a list of strings into a list of their lengths:

Without streams:

// import java.util.ArrayList;
// import java.util.List;
//
// List<String> words = List.of("apple", "banana", "cherry");
// List<Integer> lengths = new ArrayList<>();
// for (String word : words) {
//     lengths.add(word.length());
// }

With streams:

// import java.util.List;
//
// List<String> words = List.of("apple", "banana", "cherry");
// List<Integer> lengths = words.stream()  // Create a stream from the list
//                              .map(String::length) // Transform each string into its length
//                              .toList();          // Collect the result into a new list

Streams provide a rich set of operations (filtering, transformation, aggregation, etc.) that make working with collections more flexible and powerful. They are a key element of functional programming in Java and are actively used in modern applications.