question: private double boxRadius ( int i , int a , int b ) { final int level ; if ( a < 0 ) { if ( b >= pf . length ) { return Double . POSITIVE_INFINITY ; } level = maxRegLevel ( i , b ) ; } else if ( b >= pf . length ) { level = maxRegLevel ( i , a ) ; } else { level = Math . max ( maxRegLevel ( i , a ) , maxRegLevel ( i , b ) ) ; } return minDistLevel ( pf [ i ] . id , level ) ; }
target:  boxRadius function calculate the Boxradius