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java动手动脑多态
实验任务一：阅读并运行一下代码
public class ParentChildTest {
public static void main(String[] args) {
Parent parent=new Parent();
parent.printValue();
Child child=new Child();
child.printValue();
parent=child;
parent.printValue();
parent.myValue++;
parent.printValue();
((Child)parent).myValue++;
parent.printValue();
}
}
class Parent{
public int myValue=http://www.mamicode.com/100;
public void printValue() {
System.out.println("Parent.printValue(),myValue="http://www.mamicode.com/+myValue);
}
}
class Child extends Parent{
public int myValue=http://www.mamicode.com/200;
public void printValue() {
System.out.println("Child.printValue(),myValue="http://www.mamicode.com/+myValue);
}
}
程序运行结果：
为何会得到这样的输出？
（1）父类分配空间，调用自己的构造方法并输出；
（2）子类分配了空间，调用自己的构造方法，输出；
（3）子类赋值给父类，当父子类有一样的方法，父类变量引用一个子类对象，由于对象是子类，父类调用的是子类的方法，输出的是子类的值；
（4）父类中的变量进行自加运算，而且调用的还是子类的构造方法；
（5）((Child)parent).myValue++将parent对象强制转化成Child，所以指向的是Child类中的变量，输出的也是。
修改ParentChildTest.java：
public class ParentChildTest {
public static void main(String[] args) {
Parent parent=new Parent();
parent.printValue();
Child child=new Child();
child.printValue();
parent=child;
parent.printValue();
((Child)parent).myValue++;
parent.printValue();
parent.myValue++;
parent.printValue();
}
}
class Parent{
public int myValue=http://www.mamicode.com/200;
public void printValue() {
System.out.println("Parent.printValue(),myValue="http://www.mamicode.com/+myValue);
}
}
class Child extends Parent{
public int myValue=http://www.mamicode.com/300;
public void printValue() {
System.out.println("Child.printValue(),myValue="http://www.mamicode.com/+myValue);
}
}
2.模拟ATM操作系统：
package demo;
import java.util.Scanner;
class M{
String name;
String date;
String password;
int yu;
String number;
public M(String name,String date,String password,int yu,String number)
{
this.name=name;
this.date=date;
this.password=password;
this.yu=yu;
this.number=number;
}
public M(){}
public void me(){}
}
class Qukuan extends M{
public Object pasword;
public Qukuan(String str,String str1,String str2,int m,String str3){
name=str;
date=str1;
password=str2;
yu=m;
number=str3;
}
public void me(){
System.out.println("100 200 1000 1500 2000 5000 1.其它金额 2. 退卡3.返回操作");
Scanner in=new Scanner(System.in);
int p=in.nextInt();
M a=new M(name,date,password,yu,number);
if(p==100)
{
a.yu-=100;
System.out.println("取款成功,余额为:"+a.yu);
}
else if(p==200)
{
a.yu-=200;
System.out.println("取款成功,余额为:"+a.yu);
}
else if(p==500)
{
a.yu-=500;
System.out.println("取款成功,余额为:"+a.yu);
}
else if(p==1000)
{
a.yu-=1000;
System.out.println("取款成功,余额为:"+a.yu);
}
else if(p==1500)
{
a.yu-=1500;
System.out.println("取款成功,余额为:"+a.yu);
}
else if(p==2000)
{
a.yu-=2000;
System.out.println("取款成功,余额为:"+a.yu);
}
else if(p==5000)
{
a.yu-=5000;
System.out.println("取款成功,余额为:"+a.yu);
}
else if(p==1)
{
System.out.println("请输入要取款的金额:");
int m=in.nextInt();
a.yu-=m;
System.out.println("取款成功,余额:"+a.yu);
}
else if(p==2){
return;
}
else if(p==3){
me();
}
}
}
class Cunkuan extends M{
public Cunkuan(String str,String str1,String str2,int m,String str3){
name=str;
date=str1;
password=str2;
yu=m;
number=str3;
}
public void me(){
Scanner in=new Scanner(System.in);
System.out.println("请输入存款金额:");
int n=in.nextInt();
M a=new M(name,date,password,yu,number);
a.yu+=n;
System.out.println("存款成功,余额为:"+a.yu);
}
}
class Zhuanzhang extends M{
String kahao;
public Zhuanzhang(String str,String str1,String str2,int m,String str3){
name=str;
date=str1;
password=str2;
yu=m;
number=str3;
}
public void me(){
M a=new M(name,date,password,yu,number);
M B=new M("ylx","2016.11.18","123456",10000,"97093963011");
Scanner in=new Scanner(System.in);
System.out.println("请输入卡号:");
String s=in.next();
if(s.equals(number)){
System.out.println("请输入转账的金额:");
int w=in.nextInt();
a.yu-=w;
B.yu+=w;
System.out.println("转账成功!");
}
else
System.out.println("卡号输入错误!");
}
}
public class Atm {
public static void main(String args[]){
Scanner in=new Scanner(System.in);
Qukuan a1=new Qukuan("ylx","2016.11.18","123456",10000,"97093963011");
Cunkuan a2=new Cunkuan("Ylx","2016.11.17","123456",10000,"11401398081");
Zhuanzhang a3=new Zhuanzhang("mdz","2016.11.16","123456",10000,"98299363711");
System.out.println("请输入密码:");
String str=in.next();
if(a1.password.equals(str)){
while(true){
System.out.println("1 取款\n2 存款\n3 转账\n4退出");
int w=in.nextInt();
if(w==1)
a1.me();
else if(w==2)
a2.me();
else if(w==3)
a3.me();
else
break;
}
}
else
System.out.println("密码错误!");
}
}
截图：
java动手动脑多态