Java的类型转换

这一部分课本上讲的比较抽象，还是直接看代码理解的比较深刻。

public class Upcasting {    public static void main(String[] args) {        Shape s=new Shape();        s.startDraw(new Circle());        s.startDraw(new Square());        /*        Shape c=new Circle();        c.draw2(); //Error,Class Shape doesn't have Method draw2        */}class Shape{    public void draw(){    }    public void startDraw(Shape s){        s.draw();           }}class Circle extends Shape{    public void draw(){        System.out.println("draw Circle");    }    public void draw2(){        System.out.println("draw Circle2");    }}class Square extends Shape{    public void draw(){        System.out.println("draw Square");    }}