string-format: String.format/formatted/printf cheat sheet module (specifier anatomy, rounding vs C printf, locales, Indian lakh/crore grouping Formatter cannot do, format exceptions, %t dates, concat cost), 11 contract tests

Co-Authored-By: Claude Sonnet 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_017ic4b7Sr2zcoRD2watXv1G

string-format/scripts/printf_compare.c

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+/* The same four values RoundingDemo formats, through C's printf, for comparison with Java's %f. */
+#include <stdio.h>
+int main(void) {
+    printf("C printf   %%.2f of 2.675 : %.2f\n", 2.675);
+    printf("C printf   %%.1f of 0.35  : %.1f\n", 0.35);
+    printf("C printf   %%.2f of 1.005 : %.2f\n", 1.005);
+    printf("C printf   %%.2f of 0.125 : %.2f\n", 0.125);
+    return 0;
+}

string-format/scripts/run-all.sh

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+#!/usr/bin/env bash
+# Regenerates every file in output/. Timing output (07) is indicative and drifts between runs.
+set -euo pipefail
+cd "$(dirname "$0")/.."
+mvn -q -B compile
+run() { java -Dstdout.encoding=UTF-8 -cp target/classes "com.ankurm.stringformat.$1" 2>&1 | grep -v '^Picked up JAVA_TOOL_OPTIONS' > "output/$2.txt"; }
+run BasicsDemo            01-basics
+run ReportTableDemo       02-report-table
+run RoundingDemo          03-rounding
+run IndianGroupingDemo    04-indian-grouping
+run LocaleDemo            05-locale
+run FormatErrorsDemo      06-format-errors
+run FormattedAndPrintfDemo 07-formatted-printf
+run ConcatBenchmarkDemo   08-concat-benchmark
+if command -v gcc >/dev/null; then
+  gcc scripts/printf_compare.c -o /tmp/printf_compare && /tmp/printf_compare > output/10-c-printf.txt
+fi
+run DateTimeDemo          11-datetime
+mvn -B test 2>&1 | grep -E 'Tests run|BUILD|ERROR|FAIL' | grep -v 'Picked up' > output/09-tests.txt
+echo "regenerated:"; ls output

string-format/scripts/run.sh

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+#!/usr/bin/env bash
+# Run one demo: scripts/run.sh BasicsDemo
+set -euo pipefail
+cd "$(dirname "$0")/.."
+mvn -q -B compile
+java -Dstdout.encoding=UTF-8 -cp target/classes "com.ankurm.stringformat.${1:?demo class name}"