Posts (238+)

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September 2026

LZ77 and DEFLATE:Sliding-Window Compression Behind zip and gzip

Find repeated phrases in a sliding window as length-distance pairs, then Huffman-code the tokens — that pairing is DEFLATE, not Huffman alone.

Design Patterns

Template Method:Freeze the Skeleton, Vary the Steps

Freeze a shared Java payment sequence so capture, refund, and void keep one skeleton and only the provider step (and hooks) vary.

Linux

Linux ssh, scp, and Port Forwarding:Reach a Remote Box Without Guesswork

Hands-on SSH recipes — keys and config, copy files with scp, and tunnel a port without memorizing every flag.

Algorithms

Huffman Coding:Build a Prefix Code From Frequencies

Build a prefix-free code from symbol frequencies with a heap: greedy merges, why it is optimal here, and why this is not DEFLATE.

Design Patterns

Singleton:One Instance, Used Carefully

Keep a process-wide resource as an enum singleton only when you can name why there must be one, and inject Clock, config, and gateways into OrderProcessor instead of AppContext.getInstance().

Java

Lazy Constants:Initialize Once Without the Double-Checked Lock

Try JEP 531 in JDK 27: LazyConstant.of, List/Map/Set.ofLazy, and one-time thread-safe init the JIT can constant-fold — without double-checked locking.

Linux

Linux cron and systemd Timers:Run Jobs on a Schedule You Can Trust

Hands-on crontab and systemd timer recipes — schedule a job, choose calendar vs boot delays, and find the run that never fired.

Algorithms

Edit Distance:Insert, Delete, Substitute as a Costed Grid

Levenshtein distance on a DP grid: insert, delete, substitute, and recover one alignment — related to LCS, a different job.

Design Patterns

Builder:Assemble Complex Objects Step by Step

Replace a telescoping ChargeRequest constructor with a Java builder so required checkout fields stay required, optional ones stay optional, and the product can still be a record.

Linux

Linux systemctl:Start, Stop, and Debug systemd Units

Hands-on systemctl recipes for everyday work — inspect units, start and stop services, enable at boot, and debug failed units without guessing.