Java bindings (#147)

bindings/java/README.md

@@ -0,0 +1,49 @@
+# Regorus Java
+
+**Regorus** is
+
+  - *Rego*-*Rus(t)*  - A fast, light-weight [Rego](https://www.openpolicyagent.org/docs/latest/policy-language/)
+   interpreter written in Rust.
+  - *Rigorous* - A rigorous enforcer of well-defined Rego semantics.
+
+See main [Regorus page](https://github.com/microsoft/regorus) for more details about the project.
+
+Regorus can be used in Java via `com.microsoft.regorus` package. (It is not yet available in Maven Central, but can be manually built.)
+
+## Building
+
+You can build this binding using [Maven](https://maven.apache.org/):
+```shell
+$ mvn package
+$ file target/regorus-java-0.0.1*
+target/regorus-java-0.0.1-osx-aarch_64.jar: Zip archive data, at least v1.0 to extract, compression method=deflate
+target/regorus-java-0.0.1.jar:              Zip archive data, at least v1.0 to extract, compression method=deflate
+```
+
+## Usage
+
+```java
+import com.microsoft.regorus.Engine;
+
+public class Test {
+    public static void main(String[] args) {
+        try (Engine engine = new Engine()) {
+            engine.pubAddPolicy(
+                "hello.rego",
+                "package test\nmessage = concat(\", \", [input.message, data.message])"
+            );
+            engine.pubAddDataJson("{\"message\":\"World!\"}");
+            engine.pubSetInputJson("{\"message\":\"Hello\"}");
+            String resJson = engine.pubEvalQuery("data.test.message");
+
+            System.out.println(resJson);
+        }
+    }
+}
+```
+
+and run it with:
+```shell
+$ java -cp target/regorus-java-0.0.1.jar:target/regorus-java-0.0.1-osx-aarch_64.jar Test.java
+{"result":[{"expressions":[{"value":"Hello, World!","text":"data.test.message","location":{"row":1,"col":1}}]}]}
+```