question: @ Override public void put ( double val ) { final double nn = this . n + 1.0 ; final double delta = val - m1 ; final double delta_nn = delta / nn ; final double delta_nn2 = delta_nn * delta_nn ; final double inc = delta * delta_nn * this . n ; m4 += inc * delta_nn2 * ( nn * nn - 3. * nn + 3. ) + 6. * delta_nn2 * m2 - 4. * delta_nn * m3 ; m3 += inc * delta_nn * ( nn - 2 ) - 3. * delta_nn * m2 ; m2 += inc ; m1 += delta_nn ; n = nn ; min = Math . min ( min , val ) ; max = Math . max ( max , val ) ; }
target:  Add a single value with weight 1.0