question: public PooledConnection acquire ( Supplier < PooledConnection > supplier ) { PooledConnection poll = queue . poll ( ) ; if ( poll == null ) { poll = supplier . get ( ) ; } acquiredConnections . add ( poll ) ; if ( isTerminating . get ( ) ) { acquiredConnections . remove ( poll ) ; poll . dispose ( ) ; throw new IllegalStateException ( "Pool has been closed, cannot acquire new values." ) ; } return poll ; }
target:  Acquire connection or create a new one if the queue is empty