java如何使用map函数将point3d数组转换成double类型的数组

在 Java 中，我们可以使用 `Arrays.stream()` 方法将数组转换为流，然后使用 `map()` 方法将每个 `Point3D` 对象转换为对应的 `double` 数组，最后使用 `toArray()` 方法将流转换为 `double` 数组。下面是一个示例代码：

import java.util.Arrays;
import java.util.stream.Collectors;

public class Main {
    public static void main(String[] args) {
        Point3D[] points = { new Point3D(1, 2, 3), new Point3D(4, 5, 6), new Point3D(7, 8, 9) };
        double[][] doubles = Arrays.stream(points)
                .map(point3D -> new double[] { point3D.getX(), point3D.getY(), point3D.getZ() })
                .toArray(double[][]::new);
        System.out.println(Arrays.deepToString(doubles));
    }
}

class Point3D {
    private double x;
    private double y;
    private double z;

    public Point3D(double x, double y, double z) {
        this.x = x;
        this.y = y;
        this.z = z;
    }

    public double getX() {
        return x;
    }

    public void setX(double x) {
        this.x = x;
    }

    public double getY() {
        return y;
    }

    public void setY(double y) {
        this.y = y;
    }

    public double getZ() {
        return z;
    }

    public void setZ(double z) {
        this.z = z;
    }
}

输出结果为：

[[1.0, 2.0, 3.0], [4.0, 5.0, 6.0], [7.0, 8.0, 9.0]]