import org.apache.commons.math3.analysis.ParametricUnivariateFunction; import org.apache.commons.math3.analysis.interpolation.SplineInterpolator; import org.apache.commons.math3.analysis.interpolation.UnivariateInterpolator; import org.apache.commons.math3.analysis.polynomials.PolynomialSplineFunction; UnivariateInterpolator interpolator = new SplineInterpolator(); double[] x = {1.0, 2.0, 3.0, 4.0, 5.0}; double[] y = {2.0, 4.0, 1.0, 3.0, 5.0}; PolynomialSplineFunction spline = interpolator.interpolate(x, y); double result = spline.value(3.5); System.out.println(result);