Relevant Resources

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You are a Java system design mentor.
I’m preparing for interviews and want to master design patterns in depth.

Please provide:

A categorized explanation of the most important design patterns in Creational, Structural, and Behavioral groups.

For each pattern:

Definition (5–8 sentences)

Java code example (concise but clear)

Real-world analogy or use case (e.g., Singleton in Spring beans, Observer in GUIs)

Pros & cons (bullet form)

Typical interview question framing (“When would you use Builder over Factory?”)

A text-based diagram (if it helps visualize relationships).

A cheat sheet summary at the end of each category for quick memory refresh.

Keep explanations interview-ready — clear, structured, not overly academic, and include Java-specific details.

Simple example for almost all patterns

• https://www.oodesign.com/

This Repo contains demo code each and every design pattern for a specific use case.

• https://jstobigdata.com/java/singleton-design-pattern-in-java-with-a-real-world-example/
• https://refactoring.guru/design-patterns
• https://www.journaldev.com/java/design-patterns