Optional.isEmpty() does not exist in Java 8

[kanru]

Describe the bug
Using Java8, generating PlantUML diagram throws exception java.lang.NoSuchMethodError: java.util.Optional.isEmpty()Z

To Reproduce
Steps to reproduce the behavior:

1. Install JDK version 1.8.0_302
2. Run Context Mapper CLI v6.6.0 with the test.cml file (or using VSCode extension)
3. See error

Expected behavior
UML diagram is generated with no errors

Screenshots / Exceptions
Exceptions:

Exception in thread "main" java.lang.NoSuchMethodError: java.util.Optional.isEmpty()Z
	at org.contextmapper.dsl.generator.PlantUMLGenerator.getAggregatesWithStatesAndTransitions(PlantUMLGenerator.java:120)
	at org.contextmapper.dsl.generator.PlantUMLGenerator.generateFromContextMappingModel(PlantUMLGenerator.java:76)
	at org.contextmapper.dsl.generator.AbstractContextMappingModelGenerator.doGenerate(AbstractContextMappingModelGenerator.java:54)
	at org.contextmapper.dsl.standalone.StandaloneContextMapper.callGenerator(StandaloneContextMapper.java:61)
	at org.contextmapper.cli.commands.GenerateCommand.run(GenerateCommand.java:55)
	at org.contextmapper.cli.ContextMapperCLI.run(ContextMapperCLI.java:49)
	at org.contextmapper.cli.ContextMapperCLI.main(ContextMapperCLI.java:38)

Input files to reproduce

BoundedContext Test {
  Aggregate Test {
    Entity Test {
    }
  }
}

ContextMap TestMap {
  contains Test
}

IDE and Plugin (please complete the following information):

• VSCode version 1.62.0
• ContextMapper plugin version v6.6.0

Additional context
Java 11 works fine.

[stefan-ka]

Hi @kanru

Thanks for reporting this one! We fixed this with the bugfix release v6.6.1.

I'll close the issue. Let us know in case you still have problems with Java 8.

Best regards,
Stefan

FYI @socadk