Java: The Create Java Object and Invoke Java Method activities can't take empty arrays or variables initialized with "null" as arguments.

[andraciorici]

Environment
UiPath.Java.Activities 0.1.6774.30067-alpha
UiPath Studio 18.3.0-alpha.933

Preconditions

1. Create a Java project.
2. Create a Java Class with a constructor that takes a String[] as argument.
3. Create a method (static or instance) that takes a String[] as argument.
4. Package the project into a Jar file.

Steps to reproduce

1. Set the java path in the Java Scope activity.
2. Use a Create Java Object and a Invoke Java Method activities.
3. In the Parameters section of both activities create a new String[] argument.
4. In the Value field, put either {}, nothing or just leave it empty.

Expected results

• Java Object is created successfully.
• The method is executed successfully.

Actual results

• Both activities fail

Please see attachments for more details.

[viogroza]

Still reproduces on the current stable package. Here's a minimal, self-contained repro.

Environment

• UiPath.Java.Activities 2.1.1 (stable)
• Cross-platform (Portable) project, Studio 26.0
• Eclipse Adoptium JDK 25

Java fixture (com.example.ArrayHandler, packaged into a jar):

package com.example;

public class ArrayHandler {
private String[] items;
public ArrayHandler(String[] items) { this.items = items; }
public int count() { return (items == null) ? -1 : items.length; }
public static int sizeOf(String[] arr) { return (arr == null) ? -1 : arr.length; }
}

Workflow: JavaScope → LoadJar → call the constructor/methods with an empty String[] (New String(){}) and a null String[], then ConvertJavaObject.

Results

┌────────────────────────────┬────────────────────────────────┬──────────────────┬────────────────────────────────────────────────────────────┐
│ Case │ Argument │ How passed │ Outcome │
├────────────────────────────┼────────────────────────────────┼──────────────────┼────────────────────────────────────────────────────────────┤
│ static sizeOf(String[]) │ empty String[]{} │ ParametersList │ ✅ returns 0 │
├────────────────────────────┼────────────────────────────────┼──────────────────┼────────────────────────────────────────────────────────────┤
│ static sizeOf(String[]) │ null (typed String[] variable) │ typed Parameters │ ❌ AggregateException — "The method could not be invoked." │
├────────────────────────────┼────────────────────────────────┼──────────────────┼────────────────────────────────────────────────────────────┤
│ new ArrayHandler(String[]) │ empty String[]{} │ typed Parameters │ ❌ AggregateException — "Constructor could not be called." │
└────────────────────────────┴────────────────────────────────┴──────────────────┴────────────────────────────────────────────────────────────┘

So empty arrays work for the simple method via Parameters List path, but null arrays and empty-array-to-constructor still fail. Both validate and build pass — the failure is purely at runtime.

The cause looks like array parameter type/marshalling: when the array is empty or null there's no element to infer the component type from, so the empty/null branch can't resolve the declared String[] parameter and method/constructor resolution misses. A null array (or empty array) carries no runtime element to recover the type from, so the activity would need to honor the declared parameter type instead.

Repro project (jar source + XAML) available if useful.