first commit

Author: Federico-G

.claude/settings.local.json

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+{
+  "permissions": {
+    "allow": [
+      "WebFetch(domain:github.com)",
+      "WebFetch(domain:raw.githubusercontent.com)",
+      "Bash(curl:*)",
+      "WebSearch",
+      "WebFetch(domain:teavm.org)",
+      "Bash(cd:*)",
+      "WebFetch(domain:codemirror.net)"
+    ]
+  }
+}

.nojekyll

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+# TeaVM Java Support Limitations
+
+This document lists known Java APIs that don't work or have limited support in TeaVM's
+WebAssembly backend. Relevant when writing notebook examples or documentation.
+
+Reference: https://teavm.org/jcl-report/recent/jcl.html
+
+## Not Working
+
+### String Formatting
+- `String.format()` — throws error (missing Formatter/locale support)
+- `System.out.printf()` — same issue, uses Formatter internally
+- `Formatter` class — not implemented
+- **Workaround**: use string concatenation, `Math.round()` for decimal rounding
+
+### I/O & Input
+- `Scanner` — not available (no `System.in` in a browser)
+- `java.io.File`, `FileReader`, `FileWriter` — no filesystem access
+- `BufferedReader(new InputStreamReader(System.in))` — no stdin
+- **Workaround**: hardcode test values or use JS interop
+
+### Reflection
+- `Class.getDeclaredConstructor()`, `Class.getDeclaredMethod()` — throws SecurityException
+- `Method.invoke()` — not supported
+- `Class.forName()` — limited support
+- `java.lang.reflect` package — 9% fully implemented
+- **Workaround**: use TeaVM's metaprogramming API (compile-time only)
+
+### Networking
+- `java.net.URL`, `HttpURLConnection` — not supported
+- `java.net` package — 12% fully implemented
+- **Workaround**: use TeaVM's JS interop with `fetch()`
+
+### Serialization
+- `ObjectInputStream` / `ObjectOutputStream` — not supported
+- `Serializable` marker works but serialization mechanism doesn't
+
+### Class Loading
+- Custom `ClassLoader` — not supported
+- `Class.getResource()` / `getResourceAsStream()` — not available
+
+## Partially Working
+
+### Threading
+- `Thread` — emulated as green threads (coroutines), not real OS threads
+- `Thread.sleep()` — works (pauses the coroutine)
+- `synchronized` — compiles but is effectively single-threaded
+- `java.util.concurrent` — 13% fully implemented
+- `ConcurrentHashMap` — works (recent fix)
+- `AtomicReference`, `AtomicInteger`, `AtomicLong` — basic support
+- Most `Lock` classes — not available (`ReentrantLock` missing)
+
+### Streams
+- `java.util.stream` — 25% fully implemented
+- Basic `stream()`, `filter()`, `map()`, `collect()`, `reduce()` — work
+- Some collectors may be missing
+- `parallelStream()` — runs sequentially (no real threads)
+
+### Regex
+- `java.util.regex` — 50% fully implemented
+- `Pattern.compile()`, `Matcher` — basic patterns work
+- Some advanced regex features may be missing
+- Delegates to JavaScript's regex engine
+
+### Time
+- `java.time` — 63% fully implemented
+- `LocalDate`, `LocalTime`, `LocalDateTime`, `Instant` — work
+- `ZonedDateTime` — limited timezone detection
+- `DateTimeFormatter` — mostly works, some patterns may fail
+
+### Math
+- `java.math.BigDecimal` — works for basic operations
+- `java.math.BigInteger` — works for basic operations
+
+### Locale
+- Only `en_EN` locale included by default
+- Other locales need explicit configuration at compile time
+
+## Fully Working
+
+### Core
+- `java.lang.String` — all common methods (substring, charAt, indexOf, etc.)
+- `java.lang.Math` — fully supported
+- `java.lang.Integer`, `Long`, `Double`, etc. (boxing/unboxing)
+- `java.lang.StringBuilder` / `StringBuffer`
+- `java.lang.System.out.println()` — works
+- `java.lang.Exception` hierarchy — works
+- Generics, lambdas, method references — work
+
+### Collections
+- `java.util.ArrayList`, `LinkedList`
+- `java.util.HashMap`, `TreeMap`, `LinkedHashMap`
+- `java.util.HashSet`, `TreeSet`
+- `java.util.Collections` utility methods
+- `java.util.List.of()`, `Map.of()`, `Set.of()` (immutable factories)
+- `java.util.Optional`
+- `java.util.Iterator`, enhanced for-loop
+- `java.util.Arrays` — sort, fill, copyOf, etc.
+
+### Functional
+- `java.util.function` — 100% implemented
+- `Function`, `Consumer`, `Supplier`, `Predicate`, `BiFunction`, etc.
+
+### Other
+- `java.util.Objects`
+- `java.util.Random` (partial — basic nextInt/nextDouble work)
+- `java.util.zip` — jar/zip reading works (used by the compiler itself)
+- Records, sealed classes, pattern matching — compile correctly
+- `var` (local variable type inference) — works