René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"ClassCastException","articleBody":"Hello there,\r\n\r\nI tried using version 1.1.2. I installed java-oo on my Intellij IDEA and copy-pasted Example1 of yours. Now, the operators (*, +) are marked as wrong by the IDE (with the warning: `Operator '*' cannot be applied to 'symjava.symbolic.Symbol', 'symjava.symbolic.Symbol'\")`. When I try to compile, there is the following error:\r\n\r\n`java: java.lang.ClassCastException: class com.sun.proxy.$Proxy25 cannot be cast to class com.sun.tools.javac.processing.JavacProcessingEnvironment (com.sun.proxy.$Proxy25 is in unnamed module of loader java.net.URLClassLoader @2ff4acd0; com.sun.tools.javac.processing.JavacProcessingEnvironment is in module jdk.compiler of loader 'app')`\r\n\r\nDo you have an idea what might have gone wrong here? I am using Intellij IDEA 2020.3.2 (Ultimate Edition) with Java 15.0.1.","author":{"url":"https://github.com/TiMauzi","@type":"Person","name":"TiMauzi"},"datePublished":"2021-03-10T23:06:32.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":1},"url":"https://github.com/9/SymJava/issues/9"}