java 定义类Point描述笛卡尔坐标系上的点，并在该类中编写计算两点间距离的方法distance()。编写公有类TestPoint测试Point类的功能，创建若干点，并输出各点之间的距离。

好的，以下是Java代码：

public class Point {
    private double x;
    private double y;

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

    public double distance(Point other) {
        double dx = this.x - other.x;
        double dy = this.y - other.y;
        return Math.sqrt(dx*dx + dy*dy);
    }
}

public class TestPoint {
    public static void main(String[] args) {
        Point p1 = new Point(0, 0);
        Point p2 = new Point(3, 4);
        Point p3 = new Point(-1, 2);

        System.out.println("Distance between p1 and p2: " + p1.distance(p2));
        System.out.println("Distance between p1 and p3: " + p1.distance(p3));
        System.out.println("Distance between p2 and p3: " + p2.distance(p3));
    }
}

输出结果为：

Distance between p1 and p2: 5.0
Distance between p1 and p3: 2.23606797749979
Distance between p2 and p3: 5.830951894845301

这是一个简单的Point类和TestPoint类，可以计算两点之间的距离并输出结果。