how to use the Stream API in Java:
The Stream API in Java provides a functional programming approach for processing
collections of data. It allows you to perform various operations, such as filtering,
mapping, sorting, and reducing, on the elements of a collection.
To use the Stream API, you can follow these steps:
1. Create a Stream: Start by creating a stream from a collection or an array
using the `stream()` or `parallelStream()` methods.
2. Apply Intermediate Operations: Apply intermediate operations to the stream
to transform or filter the data. Examples of intermediate operations include
`filter()`, `map()`, `distinct()`, and `sorted()`.
3. Chain Operations: You can chain multiple intermediate operations together
to perform complex data transformations.
4. Apply Terminal Operation: Finally, apply a terminal operation to the stream
to get the desired result. Terminal operations consume the elements of the stream
and produce a result or a side-effect. Common terminal operations include `collect()`
, `forEach()`, `count()`, and `reduce()`.
Here's an example that demonstrates the usage of Stream API to filter and map a
list of integers:
var numbers = [1, 2, 3, 4, 5];
var result = numbers
.stream()
.filter(n => n % 2 == 0)
.map(n => n * n)
.collect(Collectors.toList());
console.log(result); // Output: [4, 16]
In the above example, we create a stream from the `numbers` array and apply the `filter()` operation to keep only the even numbers. Then, we apply the `map()` operation to square each number. Finally, we collect the result into a list using the `collect()` terminal operation.
This is just a simple example, but the Stream API can be used for much more complex data processing tasks. It promotes a more concise and expressive coding style compared to traditional loops, making your code more readable and maintainable.
