question: protected static double distance ( Solution s1 , Solution s2 ) { double distance = 0.0 ; for ( int i = 0 ; i < s1 . getNumberOfObjectives ( ) ; i ++ ) { distance += Math . pow ( s1 . getObjective ( i ) - s2 . getObjective ( i ) , 2.0 ) ; } return Math . sqrt ( distance ) ; }
target:  Returns the Euclidean distance between two solutions in objective space.