java写一个形状类，包括圆形矩形三角形

圆形，矩形，三角形，父类子类继承，重载覆盖应用

/** 父类形状**/
public class Shape{
  public void print(){
    system.out.print("a shape.");
  }
}
/** 子类三角形继承父类Shape,重写(也就是覆盖)父类print方法**/
public class Triangle extends Shape{
  @Override
  public void print(){
    system.out.print("a triangle.");
  }
}
/** 子类圆形继承父类Shape,重写父类print方法**/
public class Circle extends Shape{
  @Override
  public void print(){
    system.out.print("a Circle.");
  }
}
/** 子类圆形继承父类Shape,重写父类print方法**/
public class Rectangle extends Shape{
  @Override
  public void print(){
    system.out.print("a rectangle.");
  }
/** 重载print方法传入一个参数并打印**/
  public void print(String msg){
    system.out.print(msg + "a rectangle.");
  }
}