question: private void ensureDistances ( ) { if ( getDistanceEnd ( ) > distances . length ) { int newLength = distances . length * 4 ; double [ ] newDistances = new double [ newLength ] ; System . arraycopy ( distances , 0 , newDistances , 0 , distances . length ) ; Arrays . fill ( newDistances , distances . length , newLength , - 1 ) ; distances = newDistances ; } }
target:  Makes sure there is enough space in the distances array