java-deep-dive

Java / Spring Deep Dive

Topic-by-topic refreshers drawn from the Code Decode interview-prep library. Each file is a mid-length essay with worked Java snippets — good for a pre-interview refresher on a specific area, not a reference manual.

The content here is deeper than the TheClient-interview cards in ../theclient-interview/. If a topic appears in both places, read the TheClient card first for the bar, then come here for breadth.

Index

Java Core

File	One-liner	Maps to TheClient JD
top-java-interview-traps.md	Broad survey of Java gotchas that show up in senior interviews.	"5+ years with Java/JEE"
java-streams.md	Stream API, collectors, common pitfalls.	"5+ years with Java/JEE"
java-date-time-api.md	java.time package, Instant vs ZonedDateTime, common misuses.	"consistent JSON modeling" (ISO-8601)
records-traps.md	Java records — accessors, compact constructors, things they can't do.	"5+ years with Java/JEE"
collections-interview-traps.md	Map, Set, List API gotchas — ordering, nulls, hashCode/equals, immutability.	"5+ years with Java/JEE"

Spring / Spring Boot

File	One-liner	Maps to TheClient JD
spring-boot-traps.md	Common Spring Boot mistakes — auto-config, bean scope, transactions.	"high-performance microservices using Spring Boot"
spring-boot-rest-mistakes.md	REST-specific anti-patterns in a Spring Boot codebase.	"Own API strategy for RESTful services"
spring-boot-tricky-interview-questions.md	Senior-level Spring Boot Q&A.	"5+ years with Spring Boot"
spring-security-6-interview-questions.md	Spring Security 6 filter chain, OAuth2 resource server, common misconfigurations.	"OAuth 2.0/OIDC"

Architecture & Patterns

File	One-liner	Maps to TheClient JD
solid.md	SOLID principles with Java examples of each.	"engineering standards, design reviews, and coding best practices"
design-patterns.md	Gang-of-Four patterns that come up most in Spring codebases.	"engineering standards"
anti-patterns.md	Things to never ship. Balance the design-patterns file.	"engineering standards"
microservices-english.md	Microservice architecture — when to split, how to draw the seams.	"high-performance microservices"

Observability

File	One-liner	Maps to TheClient JD
micrometer.md	Micrometer facade, registries, OTel bridge.	"Implement observability frameworks"

Suggested reading order for a senior interview

1. top-java-interview-traps.md — covers the majority of Java-core questions in one file.
2. spring-boot-traps.md + spring-boot-tricky-interview-questions.md — Spring mental model refresh.
3. spring-security-6-interview-questions.md — directly applies to the SMART-on-FHIR / OAuth work.
4. solid.md + design-patterns.md — when the interviewer reaches for architecture-level questions.
5. micrometer.md + the TheClient OpenTelemetry card — observability story.

A note on provenance

These files started life as transcripts of the excellent Code Decode video series. They have been cleaned up for GitHub but have the narrative voice of the original — read them like a written explanation, not a spec.