support Java versions Java 9 or later

lib/td/command/workflow.rb

@@ -246,14 +246,20 @@ def detect_system_java
  return false
  end
  if output =~ /openjdk version/ or output =~ /java version/
- m = output.match(/version "(\d+)\.(\d+)\.(\d+)(?:_(\d+))"/)
+ m = output.match(/version "(\d+)\.(\d+)\.(\d+)(?:_(\d+))?"/)
  if not m or m.size < 4
  return false
  end
- # Check for at least Java 8. Let digdag itself verify revision.
  major = m[1].to_i
  minor = m[2].to_i
- if major < 1 or minor < 8
+ # Check for at least Java 8. Let digdag itself verify revision.
+ if major < 1
+ return false
+ elsif major == 1 # suppose the version style: 1.8.10_52 (JDK8 and before)
+ if minor < 8
+ return false
+ end
+ elsif major < 9 # suppose the version style: 11.0.2
  return false
  end
  end