1. // ... 创建并初始化输入数据：
2. double[] x = new double[...];
3. double[] y = new double[...];
4. 将原始的x-y数据序列合成带权重的观察点数据序列：
5. WeightedObservedPoints points = new WeightedObservedPoints();
6. // 将x-y数据元素调用points.add(x[i], y[i])加入到观察点序列中
7. // ...
8. PolynomialCurveFitter fitter = PolynomialCurveFitter.create(degree);   // degree 指定多项式阶数
9. double[] result = fitter.fit(points.toList());   // 曲线拟合，结果保存于双精度数组中，由常数项至最高次幂系数排列

package fitting;

import org.apache.commons.math3.fitting.PolynomialCurveFitter;

import org.apache.commons.math3.fitting.WeightedObservedPoints;

import java.util.ArrayList;

import java.util.List;

public class TimeCostCalculator {

    public static void main(String[] args) throws Exception {

        TimeCostCalculator tcc = new TimeCostCalculator();

        double timeCost = tcc.calcTimeCost(new CalcCurveFitting());

        System.out.println("--------------------------------------------------------------------------");

        System.out.println("time cost is: " + timeCost + "s");

        System.out.println("--------------------------------------------------------------------------");

    }

    /**

     * 计算指定对象的运行时间开销。

     *

     * @param curveFitting 指定被测对象。

     * @return 返回sub.run的时间开销，单位为s。

     * @throws Exception

     */

    public double calcTimeCost(CurveFitting curveFitting) throws Exception {

        List<Object> params = curveFitting.getParams();

        long startTime = System.nanoTime();

        Object result = curveFitting.run(params);

        long stopTime = System.nanoTime();

        curveFitting.printResult(result);

        System.out.println("start: " + startTime + " / stop: " + stopTime);

        return 1.0e-9 * (stopTime - startTime);

    }

}

interface CurveFitting {

    public List<Object> getParams();

    public Object run(List<Object> params) throws Exception;

    public void printResult(Object result);

}

class CalcCurveFitting implements CurveFitting {

    private WeightedObservedPoints points;

    private final int degree = 5;    // 阶数

    public CalcCurveFitting() {

        int arrayLength = 200000;

        System.out.println(String.format("本算例用于计算多项式曲线拟合。正在初始化计算数据（%s点，%s阶......", arrayLength, degree));

        double[] inputDataX = new double[arrayLength];

        //      inputDataX = new double[] {1, 2, 3, 4, 5, 6, 7};

        double[] inputDataY = new double[inputDataX.length];

        double[] factor = new double[degree + 1];    // N阶多项式会有N+1个系数，其中之一为常数项

        for (int index = 0; index < factor.length; index++) {

            factor[index] = index + 1;

        }

        for (int index = 0; index < inputDataY.length; index++) {

            inputDataX[index] = index * 0.00001;

            inputDataY[index] = calcPoly(inputDataX[index], factor);    // y = sum(x[n) * fact[n])

            // System.out.print(inputDataY[index] + ", ");

        }

        points = new WeightedObservedPoints();

        for (int index = 0; index < inputDataX.length; index++) {

            points.add(inputDataX[index], inputDataY[index]);

        }

        System.out.println("init completely");

    }

    @Override

    public List<Object> getParams() {

        List<Object> params = new ArrayList<Object>();

        params.add(points);

        return params;

    }

    @Override

    public Object run(List<Object> params) throws Exception {

        PolynomialCurveFitter fitter = PolynomialCurveFitter.create(degree);

        WeightedObservedPoints points = (WeightedObservedPoints) params.get(0);

        double[] result = fitter.fit(points.toList());

        return result;

    }

    @Override

    public void printResult(Object result) {

        for (double data : (double[]) result) {

            System.out.println(data);

        }

    }

    private double calcPoly(double x, double[] factor) {

        double y = 0;

        for (int deg = 0; deg < factor.length; deg++) {

            y += Math.pow(x, deg) * factor[deg];

        }

        return y;

    }

}