main类怎么定义啊

public class Distance {
    public static void main(String[] args) {
        Point pointA = new Point(0, 0);
        Point pointB = new Point(4, 3);

        Double dis = getDistance(pointA, pointB);
        System.out.println("pointA: (" + pointA.x + ", " + pointA.y + ")");
        System.out.println("pointB: (" + pointB.x + ", " + pointB.y + ")");
        System.out.println("A-B距离: " + dis);
    }

    private static Double getDistance(Point pointA, Point pointB) {
        return Math.pow((Math.pow((pointB.y - pointA.y), 2) + Math.pow((pointB.x - pointA.x), 2)), 0.5);
    }
}

class Point {
    double x;
    double y;

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