jmm: Java Memory Model companion code (volatile, happens-before, DCL)

Runnable jcstress + JUnit companion for the ankurm.com post on the
Java Memory Model, double-checked locking, and the volatile fix.

jmm/scripts/run.sh

@@ -0,0 +1,15 @@
+#!/usr/bin/env bash
+# Quick ad hoc jcstress run against one test class, printed to the terminal instead of
+# a captured output/ file. Example:
+#   ./scripts/run.sh PlainPublicationTest
+#   ./scripts/run.sh PlainPublicationTest -m tough      # extra args pass straight through
+set -euo pipefail
+cd "$(dirname "$0")/.."
+
+TEST="${1:?Usage: run.sh <TestClassName> [extra jcstress args]}"
+shift || true
+
+JAR=target/jcstress.jar
+[ -f "$JAR" ] || { echo "Run 'mvn package' first."; exit 1; }
+
+java -jar "$JAR" -t "$TEST" -jvmArgs "-Xmx256m" -f 2 -iters 15 -time 1000 -v "$@"