对象转型1
对象转型:
1、一个基类的引用类型变量可以指向其子类对象
2、一个基类的引用对象不可以访问其子类对象新增加的成员(属性和方法)
3、可以使用引用变量instanceof
4、子类的对象可以当做父类的对象称为向上转型,反之称为向下转型
例如:
package 对象转型;
class Animal{
public String name;
Animal(String name){
this.name = name;
}
}
class Cat extends Animal{
public String eyesColor;
Cat(String n,String c){
super(n);
eyesColor = c;
}
}
class Dog extends Animal{
public String furColor;
Dog(String n,String c){
super(n);
furColor = c;
}
}
class test_01 {
public static void main(String[] args) {
Animal a = new Animal("name");
Cat c = new Cat("catname","blue");
Dog d = new Dog("dog","black");
System.out.println(a instanceof Animal);
System.out.println(c instanceof Animal);
System.out.println(d instanceof Animal);
System.out.println(a instanceof Cat);
a = new Dog("bigyellow","yellow");
System.out.println(a.name);
System.out.println(a.furname); //!error
System.out.println(a instanceof Animal);
System.out.println(a instanceof Dog);
Dog d1 = (Dog)a; //要将强制转化符
System.out.println(d1.furColor);
}
}
标红的的代码内存情况是:
a = new Dog("bigyellow","yellow");
a是Animal类型的,只指向父类的,同理,只能访问父类的属性,也就是图中的name不能访问子类的属性Furcolor,如果访问的话,可以加个强制转化符,强制转换成Dag类型的
Dog d1 = (Dog)a;