question: public void moveToTail ( ) { if ( isTail ( ) || isUnlinked ( ) ) { return ; } lock . lock ( ) ; try { if ( isTail ( ) || isUnlinked ( ) ) { return ; } prev . next = next ; next . prev = prev ; next = sentinel ; prev = sentinel . prev ; sentinel . prev = this ; prev . next = this ; } finally { lock . unlock ( ) ; } }
target:  Moves the node to the tail. <p> If the node has been unlinked or is already at the tail, no-ops.