Java Interface Default Methods

Background

Default methods (Java 8+) allow adding methods to interfaces without breaking existing implementations.

Problem

Create a StringProcessor interface with a default process method that chains normalize and format, and a static factory method.

Input

A string to process through the interface.

Output

A processed string after normalization and formatting.

Sample tests

Input: "  Hello  World  "

Expected: "hello world" (trimmed and lowercased)

Your solution

Learning objective

Learn interface default methods, static factory methods in interfaces, and API evolution patterns.