In Java 8, the Stream API was introduced to provide a more functional approach to processing collections of data. One of the key features of the Stream API is the ability to use lambda expressions to write concise and expressive code. Lambda expressions allow you to define inline functions, making your code more readable and easier to maintain.

What is a lambda expression?

A lambda expression is a lightweight anonymous function that can be used to represent a behavior or a piece of code. It consists of a comma-separated list of parameters, an arrow “->”, and a body that can be a single expression or a block of statements enclosed in curly braces.

Here is the syntax for a lambda expression:

(parameter list) -> { body }

Using lambda expressions in Stream API

In the Stream API, lambda expressions are commonly used to define the behavior of the various Stream operations, such as filter, map, reduce, etc. Let’s see some examples of using lambda expressions with Stream API operations.

Filtering elements

The filter operation allows you to filter elements based on a given condition. You can use a lambda expression to define the condition.

List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);

// Filter even numbers
List<Integer> evenNumbers = numbers.stream()
                                   .filter(n -> n % 2 == 0)
                                   .collect(Collectors.toList());

Mapping elements

The map operation allows you to transform elements based on a given function. You can use a lambda expression to define the function.

List<String> names = Arrays.asList("John", "Jane", "Mary", "Mark");

// Map names to their respective lengths
List<Integer> nameLengths = names.stream()
                                 .map(name -> name.length())
                                 .collect(Collectors.toList());

Reducing elements

The reduce operation allows you to reduce a stream of elements to a single value based on a given accumulation function. You can use a lambda expression to define the accumulation function.

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

// Get the sum of all numbers
int sum = numbers.stream()
                 .reduce(0, (a, b) -> a + b);

Conclusion

Lambda expressions provide a powerful and concise way to work with Java 8 Stream API. They allow you to write more expressive code while maintaining readability. By using lambda expressions, you can easily define behaviors inline and make your code more functional.

Disclaimer: This post is for educational purposes only. Hashtags: #Java8 #LambdaExpressions