Design Patterns
Observer:Notify Dependents When Something Changes
Stop editing OrderProcessor for every new notification channel by publishing a payment event and letting EmailNotifier and AuditLog subscribe.
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September 2026
Design Patterns
Factory Method:Let Subclasses Decide Which Object to Build
Move construction of DiscountPolicy and PaymentGateway behind a polymorphic creator so six controllers stop naming PercentOff and StripeGateway.
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PEM Encodings:Keys and Certs Without the Internal Parser
What the Java 27 PEM API is (JEP 538): encode and decode keys, certificates, and CRLs with PEMEncoder and PEMDecoder — no BouncyCastle, no sun.security.util.
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Coin Change:Unbounded Combinations When the Item Can Repeat
Make change when each denomination may be used again: min-coins and count combinations, and why this is not 0/1 knapsack.
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Strategy Pattern:Swap Algorithms Without Editing Callers
Replace a growing discount if/else with a Strategy in Java so each new promotion is a class you add, not a branch you edit into OrderProcessor.
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AOT Caches:Faster Startup Without a Native Image
What Leyden AOT caches are (JEP 483, 514, 515, 516): train a HotSpot cache, then start faster and warm up sooner — still a JVM, not a GraalVM native image.
Read MoreAlgorithms
0/1 Knapsack:Pick or Skip When Each Item Exists Once
Fill a capacity with pick-or-skip DP: each item once, a 2D table or a 1D roll, and how to reconstruct which items went in.
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Design Patterns Roadmap:Pick the Right Pattern for the Pain You Have
A map of creational, structural, and behavioral patterns — what pain each one solves, when to skip it, and links to every post in this series.
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Post-Quantum TLS:Hybrid Key Exchange Before the Quantum Deadline
What Java 27 JEP 527 is: hybrid ML-KEM + ECDHE named groups in TLS 1.3 so JSSE sessions survive store-now-decrypt-later — without writing crypto.
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