[Java] rework event module #129

All 137 tests pass in 5s

137 tests +4 137 ✔️ +4 5s ⏱️ ±0s
  16 suites ±0     0 💤 ±0
  16 files ±0     0 ❌ ±0

Results for commit 45aee6c. ± Comparison against earlier commit 0857eb3.