Learn sliding window and two pointers in Java through 12 classic interview problems: fixed vs variable windows, step-by-step dry runs, brute-force cross-checks and operation counts, all from real JDK 25 runs.
Learn dynamic programming in Java from scratch: memoization vs tabulation vs space-optimised tables on ten classic problems (Fibonacci, coin change, knapsack, LCS, edit distance and more), with recursion diagrams, tested code and exact output.
A beginner-first JMH tutorial, verified on JDK 25 and JMH 1.37: dead-code elimination, Blackhole, constant folding, warmup, forks, state scopes, -prof gc and percentiles, each shown with real captured output.
Four ways to keep a password out of your Spring Boot code, each run for real on Boot 4.1.2: what happens when the secret is missing, how rotation behaves, and five ways the value leaks anyway.
Build an MCP server with only the official Java SDK 2.1.0: tools and resources, a fat jar for Claude Desktop over stdio, Streamable HTTP on Jetty, and a Spring AI client connecting to it. Every output comes from a committed transcript.
A client times out and retries a payment. Build Stripe-style Idempotency-Key handling in Spring Boot 4.1 with a Redis store and a Postgres store, and see what each does with replays, changed bodies, concurrent duplicates, expiry and a crash.
Reflection basics, why setAccessible is not a master key, what JDK 26 changes for final fields, how MethodHandles and VarHandles differ, and JMH numbers showing a call costs anywhere from 0.5 ns to 21 ns depending on one detail. Every figure comes from committed output.
Binary tree traversal in Java on one numbered nine-node tree: recursive and iterative inorder, preorder and postorder with stack dry-run tables, one-stack postorder, Morris traversal, level order and zigzag with a queue, height, an O(n) versus O(n squared) diameter comparison by counted visits, a real StackOverflowError on a one-million-node skewed tree, and exam questions with answers.
Anthropic's five agentic workflows (prompt chaining, routing, parallelization, orchestrator-workers, evaluator-optimizer) as plain Spring AI ChatClient code, tested offline with a scripted ChatModel that records every prompt, with the failure modes and the call-count cost of each.
JDK 25 already prints a warning when a library calls sun.misc.Unsafe memory-access methods, and JEP 471 plans for them to throw and then disappear. What each --sun-misc-unsafe-memory-access value does on JDK 25, how jdeps, a bytecode scan and JFR find the callers in real jars (Netty, Guava, Kryo, Hadoop, Cassandra, Protobuf and more), and CAS, off-heap and byte[] code migrated to VarHandle and the FFM API with a before/after equivalence test.