Introduction to Java 8 Features

Java 8 introduced several new features that enhance the programming experience and enable more efficient and expressive code. These features include:

• Lambdas: Lambdas provide a concise way to write code by allowing the use of anonymous functions.

• Stream API: The Stream API allows for efficient processing of collections, enabling filtering, mapping, and reducing operations.

• Default Methods: Default methods provide a way to add new methods to existing interfaces without breaking compatibility with implementing classes.

• Optional Class: The Optional class provides a way to deal with potentially null values in a more structured and safe manner.

• Date and Time API: Java 8 introduced a new Date and Time API that provides improved functionality for handling dates, times, and time zones.

• Method References: Method references allow for a more concise way to refer to existing methods and pass them as arguments.

• Functional Interfaces: Functional interfaces are interfaces with a single abstract method and can be used as the basis for lambda expressions and method references.

• Parallel Streams: Parallel streams allow for concurrent execution of stream operations, improving performance on multi-core systems.

To illustrate the usage of some of these features, here's an example of using the Stream API to calculate the sum of even numbers from a list:

1import java.util.Arrays;
2import java.util.List;
3
4public class Main {
5  public static void main(String[] args) {
6    List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5);
7    int sum = numbers.stream()
8                    .filter(n -> n % 2 == 0)
9                    .mapToInt(n -> n)
10                    .sum();
11    System.out.println(sum); // Output: 6
12  }
13}

In this example, we create a stream from a list of integers and use the filter method to filter out odd numbers. Then, we use the mapToInt method to convert the stream of integers to an IntStream and calculate the sum using the sum method. The final result is printed, which is the sum of the even numbers from the list.

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import java.util.Arrays;

import java.util.List;

​

public class Main {

  public static void main(String[] args) {

    List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5);

    int sum = numbers.stream()

                    .filter(n -> n % 2 == 0)

                    .mapToInt(n -> n)

                    .sum();

    System.out.println(sum); // Output: 6

  }

}