What is a lambda expression in Java?

A lambda expression in Java is a concise way to define anonymous methods or functions. Lambda expressions allow you to create functions without explicitly declaring a method in a class. They are used to pass behavior as arguments, store them in variables, or return them as values. The syntax of lambda expressions is simple: you specify the parameters, the arrow token (->), and the body of the function. Lambda expressions are particularly useful in functional programming as they allow for writing cleaner and more readable code, especially when working with collections and streams.

Lambda expressions bring a functional approach to Java, enabling developers to write more expressive and concise code. They eliminate the need for boilerplate code, such as the need to define anonymous inner classes, which were often used to implement single-method interfaces before Java 8. By using lambda expressions, developers can focus more on the logic they want to implement rather than on the syntax required to implement it.

Additionally, lambda expressions play a crucial role in the Java Stream API, which was also introduced in Java 8. The Stream API allows for efficient data processing, and lambda expressions make it easy to apply functions to elements of a stream. This combination of lambda expressions and the Stream API has significantly improved the way Java developers work with data collections, making their code more efficient and easier to maintain.