{"rsdb":{"rid":"156659","subhead":"","postdate":"0","aid":"117580","fid":"54","uid":"1","topic":"1","content":"

\u6211\u4eec\u5728\u4f7f\u7528\u6570\u7ec4\uff0c\u6cdb\u578b\u96c6\u5408\u7684\u8fc7\u7a0b\u4e2d\u4e0d\u53ef\u907f\u514d\u7684\u4f1a\u78b0\u5230\u591a\u6001\uff0c\u6216\u8005\u8bf4\u4ec0\u4e48\u60c5\u51b5\u4e0b\u80fd\u5982\u4f55\u4f7f\u7528\u7236\u6570\u7ec4\u5f15\u7528\u5b50\u6570\u7ec4\uff08\u96c6\u5408\u3001\u6cdb\u578b\uff09\u5462\uff1f<\/p>

\u6570\u7ec4\u5728\u591a\u6001\u4e2d\u7684\u4f7f\u7528<\/p>

\u5143\u7d20\u4e3a\u7236\u7c7b\u578b\u7684\u6570\u7ec4\u5f15\u7528\u53ef\u6307\u5411\u5143\u7d20\u4e3a\u5b50\u7c7b\u578b\u7684\u6570\u7ec4\u5bf9\u8c61<\/p>

\u5f53\u6570\u7ec4\u88ab\u8c03\u7528\u65f6\u7531\u5f53\u524d\u5f15\u7528\u786e\u5b9a\u6570\u7ec4\u5143\u7d20\u7684\u7c7b\u578b<\/p>

\u5f53\u5143\u7d20\u4e3a\u7236\u7c7b\u578b\u7684\u6570\u7ec4\u5f15\u7528\u6307\u5411\u4e86\u5143\u7d20\u4e3a\u5b50\u7c7b\u578b\u7684\u6570\u7ec4\u5bf9\u8c61\u65f6\uff0c\u4e0d\u53ef\u901a\u8fc7\u7236\u7c7b\u578b\u7684\u6570\u7ec4\u5f15\u7528\u5411\u96c6\u5408\u52a0\u5165\u9664\u5b50\u7c7b\u578b\u53ca\u5176\u4e0b\u5c42\u7ea7\u7684\u4e4b\u5916\u7684\u5143\u7d20\uff08\u53ef\u901a\u8fc7\u7f16\u8bd1\uff0c\u8fd0\u884c\u8fc7\u7a0b\u51fa\u9519\uff09<\/p>

\/*\u9a8c\u8bc1\uff1a
?*animals\u548cdogs\u53ef\u4ee5\u5f15\u7528\u540c\u4e00\u4e2a\u6570\u7ec4
?*\u5f53animals\u5f15\u7528\u6570\u7ec4\u65f6\uff0c\u6570\u7ec4\u5143\u7d20\u4e3aAnimal\u7c7b\u578b
?*\u5f53dogs\u5f15\u7528\u6570\u7ec4\u65f6\uff0c\u6570\u7ec4\u5143\u7d20\u4e3aDog\u7c7b\u578b
*\/<\/p>

public class Animal{
? ? private void showClass(){
? ? ? ? System.out.println(\"\u6570\u7ec4\u5143\u7d20\u4e3aAnimal\u7c7b\u578b\");
? ? }
? ?
? ? public static void main(String[] args){
? ? ? ? \/\/animals\u548cdogs\u53ef\u4ee5\u5f15\u7528\u540c\u4e00\u4e2a\u6570\u7ec4
? ? ? ? Dog[] dogs = {new Dog(), new Dog()};
? ? ? ? Animal[] animals = dogs;
? ? ? ?
? ? ? ? \/\/\u5f53animals\u5f15\u7528\u6570\u7ec4\u65f6\uff0c\u6570\u7ec4\u5143\u7d20\u4e3aAnimal\u7c7b\u578b
? ? ? ? animals[0].showClass();? ?
? ? ? ? \/\/\u5f53dogs\u5f15\u7528\u6570\u7ec4\u65f6\uff0c\u6570\u7ec4\u5143\u7d20\u4e3aDog\u7c7b\u578b
? ? ? ? dogs[0].showClass();
? ? ? ? \/\/\u4e0d\u53ef\u901a\u8fc7\u7236\u7c7b\u578b\u7684\u6570\u7ec4\u5f15\u7528\u5411\u96c6\u5408\u52a0\u5165\u9664\u5b50\u7c7b\u578b\u53ca\u5176\u4e0b\u5c42\u7ea7\u7684\u4e4b\u5916\u7684\u5143\u7d20\uff08\u53ef\u901a\u8fc7\u7f16\u8bd1\uff0c\u8fd0\u884c\u8fc7\u7a0b\u51fa\u9519\uff09
? ? ? ? animals[0] = new Animal();
? ? }
? ?
}<\/p>

class Dog extends Animal{
? ? public void showClass(){
? ? ? ? System.out.println(\"\u6570\u7ec4\u5143\u7d20\u4e3aDog\u7c7b\u578b\");
? ? }
}<\/p>

\u6cdb\u578b\u5728\u591a\u6001\u4e2d\u7684\u4f7f\u7528<\/p>

ArrayList<\u7236\u7c7b\u578b>\u65e0\u6cd5\u5f15\u7528ArrayList<\u5b50\u7c7b\u578b><\/p>

\/*\u9a8c\u8bc1\uff1a
?*animals\u65e0\u6cd5\u5f15\u7528dogs\u6570\u7ec4
?*
*\/
import java<\/a>.util.*;<\/p>

public class Animal{
? ?
? ? public static void main(String[] args){
? ? ? ? \/\/animals\u65e0\u6cd5\u5f15\u7528dogs\u6570\u7ec4
? ? ? ? ArrayList dogs = new ArrayList();
? ? ? ? ArrayList animals = dogs;? ? \/* \u65e0\u6cd5\u901a\u8fc7\u7f16\u8bd1 *\/
? ? }
? ?
}<\/p>


class Dog extends Animal{
? ?
}<\/p>

\u4e3a\u4e86\u5f25\u8865\u6cdb\u578b\u7684\u7f3a\u9677\uff0cjava<\/a>\u5f15\u5165\u4e86\u4e00\u79cd\u201c\u4e07\u7528\u5b57\u7b26\u201d\u2014\u2014ArrayList
\u6b64\u7c7b\u578b\u96c6\u5408\u53ef\u5f15\u7528\u4efb\u4f55\u53c2\u6570\u4e0a\u7ee7\u627f\u3001\u5b9e\u73b0\u4e86\u53c2\u6570\u7c7b\u578b\uff08\u5305\u62ec\u53c2\u6570\u7c7b\u578b\u672c\u8eab\uff09\u7684\u96c6\u5408<\/p>

\/*\u4e07\u7528\u5b57\u7b26
?*animals\u53ef\u4ee5\u5f15\u7528dogs\u96c6\u5408
?*\u5f53animals\u5f15\u7528\u96c6\u5408\u65f6\uff0c\u96c6\u5408\u5143\u7d20\u4e3aDog\u7c7b\u578b
?*\u5f53dogs\u5f15\u7528\u96c6\u5408\u65f6\uff0c\u96c6\u5408\u5143\u7d20\u4e3aDog\u7c7b\u578b
?*\u65e0\u6cd5\u901a\u8fc7animals\u5bf9\u96c6\u5408\u8fdb\u884c\u4fee\u6539
?*\/
import java.util.*;<\/p>

public class Animal{
? ? public void showClass(){
? ? ? ? System.out.println(\"\u96c6\u5408\u5143\u7d20\u4e3aAnimal\u7c7b\u578b\");
? ? }
? ?
? ? public static void main(String[] args){
? ? ? ? \/\/animals\u53ef\u4ee5\u5f15\u7528dogs\u6570\u7ec4
? ? ? ? ArrayList dogs = new ArrayList();
? ? ? ? dogs.add(new Dog());
? ? ? ? ArrayList animals = dogs;? ?
? ? ? ? \/\/\u5f53animals\u5f15\u7528\u96c6\u5408\u65f6\uff0c\u96c6\u5408\u5143\u7d20\u4e3aDog\u7c7b\u578b
? ? ? ? animals.get(0).showClass();
? ? ? ? \/\/\u5f53dogs\u5f15\u7528\u96c6\u5408\u65f6\uff0c\u96c6\u5408\u5143\u7d20\u4e3aDog\u7c7b\u578b
? ? ? ? dogs.get(0).showClass();
? ? ? ? \/\/\u65e0\u6cd5\u901a\u8fc7animals\u5bf9\u96c6\u5408\u8fdb\u884c\u4fee\u6539(\u65e0\u6cd5\u901a\u8fc7\u7f16\u8bd1)
? ? ? ? \/\/animals.add(new Dog());
? ? ? ?
? ? }
? ?
}<\/p>


class Dog extends Animal{
? ? public void showClass(){
? ? ? ? System.out.println(\"\u96c6\u5408\u5143\u7d20\u4e3aDog\u7c7b\u578b\");
? ? }
}<\/p>

\u96c6\u5408\u5728\u591a\u6001\u4e2d\u7684\u4f7f\u7528<\/p>

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