in src/main/java/org/apache/cassandra/distributed/shared/Versions.java [103:113]
public Version get(Semver version)
{
Supplier<RuntimeException> onError = () -> new RuntimeException("No version " + version.getOriginalValue() + " found");
List<Version> versions = this.versions.get(first(version));
if (versions == null)
throw onError.get();
return versions.stream()
.filter(v -> version.equals(v.version))
.findFirst()
.orElseThrow(onError);
}