sorting: Comparable vs Comparator from first principles, comparing/thenComparing/nullsFirst chaining, records as sort keys (and the record/equals compareTo trap), and a real reproduction of the int-subtraction-overflow comparator bug

Co-Authored-By: Claude Sonnet 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01YXCrLgRKFgCh9RHKW8xaqJ

sorting/scripts/run-all.sh

@@ -0,0 +1,25 @@
+#!/usr/bin/env bash
+# Regenerates every file in output/ from scratch: compile, run every demo, run the test suite.
+set -euo pipefail
+cd "$(dirname "$0")/.."
+
+mvn -q -B compile
+CP="target/classes"
+
+java -cp "$CP" com.ankurm.sorting.OldSchoolComparatorDemo 2>&1 \
+  | grep -vE 'JAVA_TOOL_OPTIONS|^WARNING' > output/01-old-school-comparator.txt
+java -cp "$CP" com.ankurm.sorting.ComparableNaturalOrderDemo 2>&1 \
+  | grep -vE 'JAVA_TOOL_OPTIONS|^WARNING' > output/02-comparable-natural-order.txt
+java -cp "$CP" com.ankurm.sorting.ComparatorFactoryMethodsDemo 2>&1 \
+  | grep -vE 'JAVA_TOOL_OPTIONS|^WARNING' > output/03-comparator-factory-methods.txt
+java -cp "$CP" com.ankurm.sorting.TreeSetOrderingDemo 2>&1 \
+  | grep -vE 'JAVA_TOOL_OPTIONS|^WARNING' > output/04-treeset-ordering.txt
+java -cp "$CP" com.ankurm.sorting.RecordOrderingDemo 2>&1 \
+  | grep -vE 'JAVA_TOOL_OPTIONS|^WARNING' > output/05-record-ordering.txt
+java -cp "$CP" com.ankurm.sorting.IntegerOverflowBugDemo 2>&1 \
+  | grep -vE 'JAVA_TOOL_OPTIONS|^WARNING' > output/06-integer-overflow-bug.txt
+
+mvn -q -B test
+cp target/surefire-reports/com.ankurm.sorting.SortingTest.txt output/07-tests.txt
+
+echo "Regenerated output/01-07."

sorting/scripts/run.sh

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+#!/usr/bin/env bash
+# Run one of the demo classes ad hoc, e.g.: ./scripts/run.sh IntegerOverflowBugDemo
+set -euo pipefail
+cd "$(dirname "$0")/.."
+mvn -q -B compile
+java -cp target/classes "com.ankurm.sorting.$1"