【程序】 class Point{ int x,y; public Point(int x, int y) { this.x = x; this.y = y; } public double distance(int x,int y){ double w=(this.x-x)*(this.x-x)+(this.y-y)*(this.y-y); return Math.sqrt(w); } public double distance(Point oth){ return distance(oth.x,oth.y); } } class Circle{ Point center; double r; public Circle(Point center, double r) { this.center = center; this.r = r; } public boolean contain(Point p){ return center.distance(p)<=r; } } public class Test { public static void main(String[] args) { Point p1=new Point(3,4); Circle c=new Circle(new Point(0,0),4); System.out.println(c.contain(p1)); } } [问题] public double distance(Point oth) 方法的返回值类型是 ( 17 ) 。