?通過覆蓋父類的方法來實現(xiàn),在運行時根據(jù)傳遞對象的引用,來調(diào)用相應的方法.
code:
class Animal
{
?int height,weight;
?Animal()
?{
??System.out.println("Animal construct");
?}
?void eat()
?{
??System.out.println("Animal eat!");
?}
?void sleep()
?{
??System.out.println("Animal sleep!");
?}
?void breathe()
?{
??System.out.println("Animal breathe!");
?}
}
class Fish extends Animal
{
?Fish()
?{
??System.out.println("Fish construct");
?}
?void breathe()? //override method breathe()
?{
??System.out.println("Fish bubble");
?}
}
class DoMain
{
?static void fn(Animal an)
?{
??an.breathe();
?}
?public static void main(String[] args)
?{
??//Animal an=new Animal();
??Fish fh=new Fish();
??Animal an;
??an=fh;
??DoMain.fn(an);
?}
}