# Java Interoperability

BoxLang compiles to JVM bytecode and runs on the JVM, so Java classes are first-class citizens. Any Java library on the classpath is usable directly from BoxLang code without glue layers or adapters.

Key interop features at a glance:

* **`java:` prefix** — force the Java class resolver: `new java:java.util.HashMap()`.
* **`new` operator** — instantiate a Java class and call its constructor in one step.
* **`createObject()`** — retrieve an uninitialized `DynamicObject`; call `.init()` to construct.
* **`extends="java:..."`** — a BoxLang class can extend a Java class; use `@overrideJava` on overriding methods.
* **`implements="java:..."`** — a BoxLang class can implement one or more Java interfaces.
* **`castAs` operator** — native type cast: `value castAs int`, `value castAs String[]`.
* **SAM auto-coercion** — closures, lambdas, and UDFs passed to `@FunctionalInterface` parameters are auto-wrapped; no proxy needed.
* **BIFs** — `CreateObject`, `JavaCast`, `CreateDynamicProxy`, `IsInstanceOf`, `GetBoxContext`, and more.

For the complete reference — class resolution, coercion strategies, inheritance, dynamic proxies, custom class loaders, and Mermaid architecture diagrams — see the full guide:

{% content-ref url="/pages/6RbGtbPRMz5i3Z1cBvum" %}
[Java Interop](/boxlang-framework/java-integration.md)
{% endcontent-ref %}


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