What are lambda expressions in Java and what capabilities do they provide?

Lambda expressions in Java are anonymous functions that allow for more concise code, especially when working with functional interfaces. They consist of a parameter block, the arrow ->, and the function body.

Main features:

• Code reduction: Eliminate the need to create anonymous inner classes for implementing functional interfaces.
• Functional programming: Simplify the application of functional programming concepts, such as passing functions as arguments.
• Improved readability: In some cases, make the code more understandable and easier to perceive.
• Working with Stream API: They are fundamental for efficient data stream processing in Java 8 and above.

Example:

// Traditional way with an anonymous class
Runnable traditionalRunnable = new Runnable() {
    @Override
    public void run() {
        System.out.println("Hello from traditional runnable");
    }
};

// Using a lambda expression
Runnable lambdaRunnable = () -> System.out.println("Hello from lambda runnable");

A lambda expression is bound to a functional interface – an interface with a single abstract method. The parameter types and return value of the lambda are determined by the signature of this abstract method.