51类的继承—子类的定义示例 class Point∥/点类 protected int x,y;//点坐标 public Point(t //无参构造方法 public Point(int xx, int yytsetPoint(xx, yyi public void setPoint(int m, int n){x=my=n}/设置标位置 public int getxotreturn X;] public int getYotreturn yi] 继承于点 类的圆类 class Circle extends point//定义圆类 private double radius / radius为圆的半径 public Circle(int x,int y, double r)this x=X; thisy=y; setRadius(r)il public void setRadius( double r) radius=r;}//设置圆的半径 public double getRadiuso{ return radius}//获取圆的半径 public double getAreaotreturn3.1415* radius* radius;//获取圆 的面积class Point{ //点类 protected int x,y; //点坐标 public Point(){} //无参构造方法 public Point(int xx,int yy){setPoint(xx,yy);} public void setPoint(int m,int n){x=m;y=n;} //设置标位置 public int getX(){return x;} public int getY(){return y;} } class Circle extends Point{ //定义圆类 private double radius; //radius为圆的半径 public Circle(int x,int y,double r){this.x=x;this.y=y;setRadius(r);} public void setRadius(double r){radius=r;} //设置圆的半径 public double getRadius(){return radius;} //获取圆的半径 public double getArea(){return 3.1415*radius*radius;} //获取圆 的面积 5.1 类的继承——子类的定义示例 继承于点 类的圆类