How do you use lambda expressions with collections?
Table of Contents
Introduction
Lambda expressions in Java provide a concise way to express instances of single-method interfaces (functional interfaces). When combined with collections, they enable powerful and expressive operations such as filtering, transforming, and iterating over data. This guide explores how to use lambda expressions with various Java collections, including lists, sets, and maps.
Using Lambda Expressions with Different Collections
1. Working with Lists
Lists are one of the most commonly used collections in Java. You can utilize lambda expressions with the forEach method to iterate over list elements easily.
Example: Iterating over a List
In this example, the forEach method iterates through the list, applying the lambda expression to each element.
2. Filtering a List with Streams
Lambda expressions work seamlessly with the Stream API, allowing for filtering and transformation of lists.
Example: Filtering a List
Here, the filter method uses a lambda expression to check each name, collecting those that start with "C".
3. Working with Sets
Lambda expressions can also be applied to sets, allowing for similar operations as with lists.
Example: Iterating over a Set
In this case, the lambda expression prints each integer from the set.
4. Transforming a Map
Lambda expressions are useful for transforming map entries as well.
Example: Iterating over a Map
This example demonstrates how to iterate over a map's key-value pairs using a lambda expression.
Conclusion
Lambda expressions significantly enhance how you interact with Java collections. They enable concise, readable, and efficient code, particularly when combined with the Stream API for operations like filtering, mapping, and iterating. Mastering the use of lambda expressions with collections is essential for leveraging the full power of modern Java programming.