用Java实现Apache通用数学的数值二重积分

import org.apache.commons.math3.analysis.integration.*;
import org.apache.commons.math3.analysis.function.*;

BivariateFunction function = new BivariateFunction() {
    public double value(double x, double y) {
        // 在这里定义二元函数的表达式
        return x * y;
    }
};

double xLower = 0.0;  // x的下限
double xUpper = 1.0;  // x的上限
double yLower = 0.0;  // y的下限
double yUpper = 2.0;  // y的上限

IterativeLegendreGaussIntegrator integrator = new IterativeLegendreGaussIntegrator(5, 1e-6, 1e-6);
double result = integrator.integrate(100, function, xLower, xUpper, yLower, yUpper);

System.out.println("数值二重积分结果：" + result);