Jackson 3 series companion code

37 runnable examples covering the eight feature posts on ankurm.com, verified
against Jackson 3.2.1 on Temurin 21.0.5. Every output committed under docs/ was
produced by run-all.sh.

Also documents 11 places where the published snippets do not compile or do not
behave as printed against a real Jackson 3 build - most notably that
writeValueAsString(List<Base>) silently drops the polymorphic type discriminator,
so the post's serialised output cannot be read back.

run-all.sh

@@ -0,0 +1,27 @@
+#!/usr/bin/env bash
+# Compiles the project and runs every example, writing each program's real output
+# to docs/output/<ClassName>.txt. Everything checked into docs/output was produced
+# by this script — nothing is hand-written.
+set -u
+cd "$(dirname "$0")"
+
+mvn -B -q clean compile || { echo "compile failed"; exit 1; }
+CP="target/classes:$(mvn -B -q dependency:build-classpath -Dmdep.outputFile=/dev/stdout -DincludeScope=runtime 2>/dev/null | tail -1)"
+mkdir -p docs/output
+
+FAILED=0
+for f in $(find src/main/java -name '*.java' | sort); do
+  CLASS=$(echo "$f" | sed 's|src/main/java/||; s|\.java$||; s|/|.|g')
+  grep -q 'public static void main' "$f" || continue
+  SHORT="${CLASS##*.}"
+  printf '%-52s' "$SHORT"
+  if java -cp "$CP" "$CLASS" > "docs/output/$SHORT.txt" 2>&1; then
+    echo "ok"
+  else
+    echo "FAILED"; FAILED=1
+  fi
+done
+
+echo
+if [ "$FAILED" -eq 0 ]; then echo "All examples ran successfully."; else echo "Some examples failed."; fi
+exit $FAILED