Object REXX and Java 17: Resolving Overloaded Methods with Primitive Arguments

Understanding the Dispatch Ambiguity

p>When integrating Object REXX with Java 17, the primary challenge lies in the gap between REXX's untyped variable system and Java's strict method signature matching. When a REXX variable is passed to a Java method with overloaded signatures, the dispatcher must decide which specific primitive type (e.g., int, long, double) to map the value to.

In Object REXX 5.0+, while native coercion handles many basic cases, it is not always deterministic when multiple overloads exist. If a Java class provides both process(int) and process(double), passing a REXX numeric literal may resolve differently depending on the internal state of the dispatcher or version, leading to inconsistent behavior across different runtime environments.

Strategies for Deterministic Resolution

To ensure the correct method is invoked and avoid runtime exceptions, follow these practices:

1. Explicit Type Casting: Instead of relying on the dispatcher to guess the type, cast the REXX variable to the required wrapper class before passing it. This forces the dispatcher to use the specific primitive overload.

   ; val = 10; myObject.method(Integer(val)); 

2. Wrapper Instantiation: If the method expects an object, explicitly instantiate the wrapper in REXX to bypasses the primitive-to-object auto-boxing logic entirely.
3. Avoid Ambiguous Signatures: If you control the Java API, avoid exposing both String and StringBuilder variants alongside primitive overloads, as the REXX-to-Java conversion rules for these types can be complex during automated dispatch.

Exception Handling and Versioning

Regarding errors, checked Java exceptions thrown during primitive dispatch are generally converted to a REXX RuntimeException. However, the specific trap behavior—whether it triggers a SIGNAL or terminates the exec—can vary based on how the REXX distribution handles the Java stack trace.

These assumptions assume you are using Object REXX 5.0+ on a Java 17 runtime. Older distributions restricted to Java 8 will not encounter module-path issues but may also exhibit different primitive mapping logic due to the older JVM dispatcher behavior.

Verification Command

To verify how your specific environment resolves an overload, run a test exec with a controlled Java class:

; Test class has methods test(int) and test(double)
t = new TestClass();
nt.test(5);
t.test(5.5);