Java 8 - Stream

Java 8 - Streams

Java 8 Streams are a powerful feature that allows us to work with collections in a more functional and declarative way. Streams provide a set of methods that allow us to perform operations on a collection of elements, such as filtering, mapping, and reducing. In this blog, we will explore what Java 8 Streams are, why they are useful, and how to use them in Java with code examples.

What are Java 8 Streams?

In Java, a stream is a sequence of elements that can be processed in parallel or sequentially. Streams can be created from collections, arrays, and I/O channels. Streams provide a way to express complex operations on collections in a functional and declarative way. They can be used to filter, map, and reduce elements in a collection, as well as to perform more complex operations such as grouping, sorting, and joining.

Why are Java 8 Streams useful?

Java 8 Streams are useful because they provide a more declarative way to work with collections. Streams allow us to express complex operations in a more functional way, which can make our code more readable and maintainable. They also allow us to parallelize our code more easily, which can improve performance in some cases. Additionally, streams provide a more efficient way to process large collections of data by avoiding the need to store intermediate results in memory.

How to use Java 8 Streams in Java

To use Java 8 Streams in Java, we need to follow these three steps:

1: Create a Stream To create a stream in Java, we can use the stream() method on a collection or the Arrays.stream() method on an array. Here’s an example:

List<String> names = Arrays.asList("Alice", "Bob", "Charlie");
Stream<String> stream = names.stream();

In this example, we create a stream from a list of strings called names.

2:Perform Operations on the Stream Once we have created a stream, we can perform operations on it. The two types of operations that can be performed on a stream are intermediate operations and terminal operations.

Intermediate operations are operations that transform the stream into another stream, such as filter(), map(), and flatMap(). These operations do not produce any final results.

Terminal operations are operations that produce a final result from the stream, such as forEach(), reduce(), and collect(). These operations terminate the stream.

Here’s an example of how to perform operations on a stream:

Stream<String> stream = names.stream()
    .filter(name -> name.length() > 3)
    .map(name -> name.toUpperCase())
    .sorted();

Stream<String> stream = names.stream()
    .filter(name -> name.length() > 3)
    .map(name -> name.toUpperCase())
    .sorted();

In this example, we create a stream from the names list and apply three intermediate operations (filter(), map(), and sorted()) to transform the stream. The resulting stream will contain all names with more than three characters, converted to uppercase, and sorted alphabetically.

3:Collect the Result

Once we have performed operations on a stream, we can collect the result using the collect() method. Here’s an example:

List<String> result = stream.collect(Collectors.toList());

In this example, we collect the result of the stream operation into a list called result.

Conclusion

Java 8 Streams are a powerful feature that can make our code more readable, maintainable, and efficient. By using streams, we can express complex operations on collections in a more functional and declarative way. We can also parallelize our code more easily, which can improve performance. By mastering the use of Java 8 Streams, you can write code that is more efficient, more maintainable, and easier to read.