kingchenc
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Adds a Java binding (`bindings/java`) over the C ABI hub — the fourth language stecker after C#, Go and R, reaching the hub through the Java Foreign Function & Memory API (Panama, `java.lang.foreign`, final in Java 22) rather than JNI or jextract. ## What's here - **`bindings/java`** — a Maven module (`org.wickra:wickra`) exposing all 514 indicators as idiomatic `AutoCloseable` classes. The downcall handles (`internal/NativeMethods.java`), the per-indicator wrappers and the output records are generated from `bindings/c/include/wickra.h` (same eight-archetype taxonomy as the C#/Go/R generators: scalar/batch, multi-output, bars, profile, values-profile, array-input). The opaque handle is a `MemorySegment` freed by a registered `java.lang.ref.Cleaner` action; multi-output returns a `record` (`null` at warmup), bars a `record[]`, profiles a record with a trailing `double[]`. The hand-written `WickraNative` resolves the native library (a bundled per-platform copy, or a `target/release` fallback for local development) and validates it against a sentinel symbol. repr(C) struct offsets are computed in the generator so the FFM reads land on the exact bytes. - **`examples/java`** — the full example suite mirroring C/C#/Go/R: streaming, backtest, multi_timeframe, parallel_assets (parallel streams), three strategies, and `FetchBtcusdt`/`LiveBinance`. - **CI** — a `java` job builds the C ABI library, sets up JDK 22 (Temurin, with a CDN-flake retry), runs the archetype test suite and the seven offline examples on Linux, macOS and Windows. - **Release** — a gated `java-publish` job (skipped until the `JAVA_PUBLISH_ENABLED` repository variable is set) stages the native libraries from the `wickra-c-<triple>.tar.gz` assets into the binding's resources and deploys to Maven Central with GPG signing. Independent of the GitHub-release job, like the NuGet job. - **Docs** — Java added to the README languages table, project layout, building/testing and comparison table, CONTRIBUTING, ARCHITECTURE, the examples index, the issue/PR templates, the About-description template, and the other binding READMEs. ## Requirements Java 22+ (the FFM API is final since Java 22). The binding requires `--enable-native-access=ALL-UNNAMED` at runtime; the test and example runners pass it automatically. No Rust crate or `Cargo.toml` change — the Java binding is standalone and additive. The generated `*.java` are committed (like the node `index.js`/`index.d.ts`); the generator stays private.
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Wickra examples — Java
Runnable examples for the Wickra Java binding. Each
example is a small main class that uses the org.wickra:wickra artifact and
resolves the native library automatically (from target/release during local
development, or the bundled per-platform library when packaged).
Build the native library and install the binding to your local Maven repo
first, then run any example with the exec plugin:
cargo build -p wickra-c --release
mvn -f bindings/java install -DskipTests
mvn -f examples/java compile
mvn -f examples/java exec:exec -Dexec.mainClass=org.wickra.examples.Streaming
(The exec:exec goal forks a JVM with --enable-native-access=ALL-UNNAMED, the
flag the FFM API needs.)
| Example | What it does | Main class |
|---|---|---|
streaming |
Feed a synthetic price series through SMA / EMA / RSI / MACD tick by tick. | org.wickra.examples.Streaming |
backtest |
Compute a basket of indicators over an OHLCV series and print a summary. | org.wickra.examples.Backtest |
multi_timeframe |
Resample a 1-minute series into 5m / 15m and print an indicator per timeframe. | org.wickra.examples.MultiTimeframe |
parallel_assets |
SMA(20) batch over a panel of assets, serial vs parallel streams, with speedup. | org.wickra.examples.ParallelAssets |
strategy_rsi_mean_reversion |
RSI(14) mean-reversion with a PnL / Sharpe / max-DD summary. | org.wickra.examples.StrategyRsiMeanReversion |
strategy_macd_adx |
MACD crossover entries gated by ADX(14) > 20. | org.wickra.examples.StrategyMacdAdx |
strategy_bollinger_squeeze |
Bollinger-squeeze breakout with an ATR(14) trailing stop. | org.wickra.examples.StrategyBollingerSqueeze |
fetch_btcusdt |
Download real BTCUSDT klines from the Binance REST API into a CSV. | org.wickra.examples.FetchBtcusdt |
live_binance |
Stream live Binance klines through EMA(20) over a WebSocket. | org.wickra.examples.LiveBinance |
fetch_btcusdt and live_binance require network access; the rest run offline
on deterministic synthetic data. Shared helpers (synthetic data, CSV loader,
equity summary) live in MarketData and Equity.