Java多态

package myNote;class BaseClass//一个里面只能有一个public class{public int book = 6;public void base(){System.out.println("父类函数");}public void test(){System.out.println("父类方法test");}}public class SubClass extends BaseClass {public String book = "子类book";public void test(){System.out.println("子类的方法test");}public void sub(){System.out.println("子类自己的方法");}public static void main(String[] args){BaseClass base = new BaseClass();System.out.println(base.book);base.base();base.test();SubClass sc = new SubClass();System.out.println(sc.book);sc.test();sc.sub();BaseClass ploy = new SubClass(); //用父类的引用接收子类的构造System.out.println(ploy.book);//输出父类的 6 ploy.test();//子类的方法test   执行了子类方法ploy.base();//父类函数   执行父类方法}}