c.java

来自「java课件及例程有一些PPT及一些例程」· Java 代码 · 共 28 行

class A
{
    int x=3;
    public void m()
    {
        System.out.println("the x of A is "+x);
    }
}
class B extends A
{
    double y=2;  
    public void n()
    {
        y--;
        System.out.println("y= "+y+",x= "+x);  
    }    
}
class C{
    public static void main(String[] args)
    {
        B ref_b;
        B b = new B();
        A a;
        a=b;
        ref_b=(B)a;       	
    }
}