JRException error "java.util.ArrayList"

[peter...@googlemail.com]

Hello, when running my tiny jrxml template in Memento on Windows 10, I get a JRException error “Unknown image source class java.util.ArrayList”. The template refers to the image stored in the Memento blob:

    <field name="Bild, Smartphone" class="java.util.ArrayList"/>

I just installed the Java Dev Kit 25.0.2. (64 bit) and Memento 3.8.0 is also 64 bit. I have hardly any Java knowledge. Can this be a Java configuration error on my machine? Thanks for tips.