Hello,
if I try to write a Rule as following:
rule "Initialize on System start"
when
System started
then
HashMap<String,String> myMap = new HashMap
end
the Log Message “Error during the execution of startup rule ‘Initialize on System start’ : null” comes after saving the rule. But why? Can’t I initialize a Map on System start?
Okay, at this point it was my fault. The initialization of the HashMap must be like:
HashMap<String,String> myMap = newHashMap
But now there is a new error message in the log:
“‘get’ is not a member of ‘java.util.HashMap’”
What does it mean? I want to use the command:
myMap.get("MyKey")
I’m surprised you are not selling syntax errors. You are missing the val. Also, defining it is a System started rule doesn’t do much for you as any variable defined in a Rule goes away as soon as the Rule exits.
You need to define it as a global if you want to use it across multiple Rules.
https://docs.openhab.org/configuration/rules-dsl.html#the-syntax
Finally, in my experience, there is usually a better way to achieve whatever you are after using Items and Groups and the Design Patterns.