// Java · Spring · Kafka · Algorithms

Practical guides to Java, Spring and algorithms, with code you can run.

Each article explains one topic around a complete example you can copy and run.

Browse algorithms Java how-tos

Java

static int fibonacciOptimized(int n) {
  int prev1 = 1;
  int prev2 = 1;
  for(int i=2; i<=n; i++) {
      int currentFib = prev1 + prev2;
      prev1 = prev2;
      prev2 = currentFib;
  }
  return prev2;
}

Fibonacci in O(n) time and O(1) space. See how it is derived

569

algorithm problems

126

Java articles

54

Spring articles

21

problem categories

Browse by topic

569 problems Algorithms Patterns and solutions in Java, organised by data structure and technique. 126 articles Java Collections, IO, concurrency, modern Java and the JVM. 54 articles Spring Core, Spring Boot, data access, security and Spring Cloud. 19 articles Kafka Producers, consumers, topics, partitions and operations. 15 articles Apache Camel Routes, integration patterns and connectors. 5 articles DevOps Docker, Kubernetes and Helm for Java services.

Popular articles

Algorithms LRU Cache: Design & Implementation Build an O(1) LRU cache using a doubly-linked list combined with a HashMap. Spring Boot Building REST APIs with @RestController GET, POST, PUT, DELETE endpoints with path variables, request bodies and ResponseEntity. Java 21 Java Virtual Threads: Project Loom Lightweight threads for blocking code: how virtual threads work and when to use them. Algorithms Dynamic Programming: Introduction Memoization vs tabulation, recognising overlapping subproblems, general templates. Spring Aspect Oriented Programming (AOP) Logging, performance timing and cross-cutting concerns with @Aspect and @Around. Kafka Kafka: Architecture Introduction Producers, consumers, brokers, topics and partitions explained with diagrams.

Algorithm problems by category

All 569 problems

Arrays 90 Strings 47 Dynamic programming 41 Graphs 39 Trees 34 Sliding window 30 Binary search 26 Two pointers 22 Heap and priority queue 21 Backtracking 20 Design 15

From the blog

Nov 8, 2026 · Janardhan Chejarla Debug Logs for Every Failed Request Production services log at INFO, so when a request fails, the DEBUG lines that would explain it were never written. Why I built debug-on-failure, how it keeps DEBUG lines only for failed requests, and what it costs.