Explore the single responsibility principle by building a Java palindrome counter that counts palindrome words in a sentence, with a simple reverse-check method and a clear srp-focused design.

Refactor the palindrome counter by applying SRP, extracting sentence splitting into a sentence splitter class and a palindrome checker, and wiring dependencies to enable single responsibility.

Learn the open for extension and closed for modification principle (OCP) and how to extend functionality without modifying existing code. Explore a real-world Eclipse plugin example that shows seamless integration.

Explore applying the open/closed principle to username validation by splitting logic into separate validator classes and orchestrating them via a shared interface in a single username validator.

Apply preconditions to validate itinerary and future travel date before discount logic executes. Enforce postconditions to guarantee non-zero, sensible discounts and provide a guaranteed discount retrieval method.

Understand how strengthening preconditions in a subtype breaches LSP, as shown by the airline discount calculator example, and how weakening may align behavior with business rules.

Explains the Liskov Substitution Principle through an invariant guideline with a discount calculator example, showing how a subtype must preserve the supertype invariants to avoid side effects.

Explore how the LSP history constraint prevents state changes to the guaranteed discount and guides safe subclassing by preserving supertype behavior and using private fields.

Explore the dependency inversion principle, differentiate high level and low level modules via abstractions, and examine source code dependency trees and their downsides like propagation, deployment impact, and tight coupling.