Java是一種非常流行的編程語言，用于開發各種不同類型的應用程序。其中，與點和圓相關的應用程序也廣泛存在。在Java中，點和圓之間的關系可以通過距離公式來計算。

public class Point {
private double x;
private double y;
public Point(double x, double y) {
this.x = x;
this.y = y;
}
public double getX() {
return x;
}
public double getY() {
return y;
}
public double distanceTo(Point point) {
double dx = point.getX() - x;
double dy = point.getY() - y;
return Math.sqrt(dx*dx + dy*dy);
}
}
public class Circle {
private Point center;
private double radius;
public Circle(Point center, double radius) {
this.center = center;
this.radius = radius;
}
public Point getCenter() {
return center;
}
public double getRadius() {
return radius;
}
public boolean contains(Point point) {
double distance = center.distanceTo(point);
return (distance<= radius);
}
}
public class Main {
public static void main(String[] args) {
Point p1 = new Point(0, 0);
Point p2 = new Point(3, 4);
double distance = p1.distanceTo(p2);
System.out.println("Distance between p1 and p2: " + distance);
Circle circle = new Circle(new Point(1, 2), 5);
System.out.println("Circle contains p1? " + circle.contains(p1));
System.out.println("Circle contains p2? " + circle.contains(p2));
}
}

上述代碼定義了一個Point類和Circle類，分別表示點和圓。Point類主要用于計算點與點之間的距離，而Circle類則用于判斷一個點是否在圓內。Main類用于測試上述兩個類的功能，輸出了點之間的距離和點是否在圓內的判斷結果。