为什么在删除废弃的连接时，Apache DBCP池在criteira下面？
Abandonded connections are identified and removed when getConnection() is
invoked and the following conditions hold
getRemoveAbandoned() = true
getNumActive() > getMaxActive() - 3
getNumIdle() < 2
为什么这些魔术数字2和3？谁能解释？