??????????????￡?Java??????????????????
????1?? ???
????2?? ??????д??????
????3?? ??????????????????
??????????????
package test.xing;
class Father{
protected int age;
public Father(){
age = 40;
}
void eat(){
System.out.println("????????");
}
}
class Child extends Father{
protected int age;
public Child(){
age = 18;
}
void eat(){
System.out.println("????????");
}
void play(){
System.out.println("???????CS");
}
}
public class TestPolymorphic {
public static void main(String[] args) {
Father c = new Child();
c.eat();
//c.play();
System.out.println("????"+c.age );
}
}
?????????????

?????????????????Java???????????????????????c.eat()?????????????????eat????c.age????????????age????c.play()???????????
?????????JVM???????????????????
?????????Father c = new Child()??仰????
??????仰????????new Child()??????з??????????
????????????Child???????????????JVM???????????Child??????class????????JVM?У????JVM????class????е????????????????class?????????????????
????????????????????????JVM???в???????????????????????????????JVM??淶??
??????????class??????????????????????????????????
????1?? ??????
????2?? ????????????????
????3?? ??????
????4?? ???????
????5?? ?????????
????6?? ??????????????
??????Щ?????????????????????????JVM?????鼮?硶???????Java????????????????и????????á?
???????JVM?????????????????????????????????????????????????????java?????????????
???????????а??????????????????????????????????????????????Щ??????????????????????????????????????????????????????
???????????Щ????????????????????????????????丸???????????????????????????????????????Object????
???????????Щ?????в???????з??????????з????????У?
???????????е???Щ??????????JVM?б?????????????????壨????????????壩??????????????????????????4?????λ?????????????????????????л??и??????????????????????????????????λ?á?
???????????????????????滭????????

?????????????????????в?????????????????????????????????????????????????????Child?????????????
??????????????У?????????????Object???????????????Щ???????toString??????equals??????Object?л????????????????д??
????????????в??????????Parent??????????????????eat??
???????????????????????á?
???????????????????????Child??????????????Parent???е???????????????????????eat???????????????????????????????????????????eat?????????????μ??????????е????????????????Parent.eat???????????滻?????Child.eat????????????????е?λ??????????????????Child????????????????Child.eat??Parent????????????????Parent.eat????????????????????Parent.eat?????????
??????????????????????Parent??Child????????У????eat??????????е???????????????????????λ?á??????????????eat??????????????eat??????????????????eat??????????????е?λ???
???????????????????????????????У???????????????????????е??????????д????????????и????????????
??????????????????????????????ж?????

?????????????????????Father????????????????????????е?Child????????
??????????????????Father c????壬???????c???????????????????????е?Child??????????????????????????????????е?Child??????????????????????????滹?????Father???????c
??????????????c????void????????????????????????????????????????????????????char * p???p?????????????????????棬????int *p??p??????????????????????檔
??????????????????????????????????????????????????????????з?????????????char *?????????p???????????????????????????????????С??????????????????????????
??????????java????????Father?????????c?????????????棬??漲????????????????С??
?????????Father?????????С??????У???Child???????????У??????????????￡???
???????????c??????Child????????????????Father????????????????????е??????????c???????????Child???е?age?????????????Father???age?????????40
????????????????????????????

???????????Parent???????????У?Child????????4?У?c????????Child???????????????????????????Child?????????????????c?????Father?????Σ????c????????Child?????????3?е????????????
????????????????????????γ?????У???????д??????????????????????????Child???????????????????Child.eat????????????????Parent.eat??????????????????????????c?????????Child.eat???????????????????????????￡?c????а?????????????eat???????
???????????????????????
?????????????????俴JVM??????????ò??????????????????????лл??