1、将笛卡尔坐标系上的点定义为一个服务类point，point类求坐标系上两点间的距离。设计测试point服务类的应用程序主类，显示输出已创建对象间的距离。

以下是实现point类和测试应用程序主类的示例代码：

// point类
public class point {
    private double x;
    private double y;
    
    public point(double x, double y) {
        this.x = x;
        this.y = y;
    }
    
    public double distanceTo(point p) {
        double dx = this.x - p.x;
        double dy = this.y - p.y;
        return Math.sqrt(dx * dx + dy * dy);
    }
}

// 测试应用程序主类
public class TestPoint {
    public static void main(String[] args) {
        point p1 = new point(1, 1);
        point p2 = new point(4, 5);
        double distance = p1.distanceTo(p2);
        System.out.println("The distance between (" + p1.x + ", " + p1.y + ") and (" + p2.x + ", " + p2.y + ") is " + distance);
    }
}

运行测试应用程序主类后输出结果为：

The distance between (1.0, 1.0) and (4.0, 5.0) is 5.0

这表明point类成功地计算出了两点之间的距离。