08 多态与异常处理

课后作业一：接口多态：使用接口代替抽象基类
一、源代码
package zoo4;

import java.util.Vector;

public class Zoo2 {

    public static void main(String args[]) {
        Feeder f = new Feeder("小李");
        Vector<Animal> ans = new Vector<Animal>();//可随时向其中加入或移除对象

        //饲养员小李喂养一只狮子
        ans.add(new Lion());
        //饲养员小李喂养十只猴子
        for (int i = 0; i < 10; i++) {
            ans.add(new Monkey());
        }
        //饲养员小李喂养5只鸽子
        for (int i = 0; i < 5; i++) {
            ans.add(new Pigeon());
        }
        f.feedAnimals(ans);
    }
}

class Feeder {

    public String name;

    Feeder(String name) {
        this.name = name;
    }

    public void feedAnimals(Vector<Animal> ans) {
        for (Animal an : ans) {
            an.eat();
        }
    }
}

interface Animal {

    public void eat();
}

class Lion implements Animal {

    public void eat() {
        System.out.println("我不吃肉谁敢吃肉！");
    }
}

class Monkey implements Animal {

    public void eat() {
        System.out.println("我什么都吃，尤其喜欢香蕉。");
    }
}

class Pigeon implements Animal {

    public void eat() {
        System.out.println("我要减肥，所以每天只吃一点大米。");
    }
}

二、实验运行截图

课后作业二：用多态的方法模拟ATM操作流程

1.源程序：

package Work;
//接口多态：使用接口代替抽象基类

import java.util.Scanner;
import java.util.Vector;

public class ATM{
    static AccountY stu[]=new Account[500];
    
    public static void main(String[] args) {
        
        //主界面(5个用户)
        stu[0]=new Account("20153149","流刘雨鑫","2016/11/16","12346",100);
        stu[1]=new Account("20153150","刘","2016/11/15","li",2000);
        stu[2]=new Account("20153151","啦啦子","2016/11/15","muzi",3000);
        stu[3]=new Account("20153149","咦米","2016/11/15","mimi",5000);
        stu[4]=new Account("20153148","哦哦暑","2016/11/15","xiaxiao",40);
        String key;
        Scanner scan=new Scanner(System.in);
        Scanner scan1=new Scanner(System.in);
        Scanner scan2=new Scanner(System.in);
        Scanner scan3=new Scanner(System.in);
        int num=0;
        int k=1;
        System.out.println("请输入密码：");
        key=scan.nextLine();
         int b=0;
          for(int i=0;i< 5;i++)
          {  if(!key.equals(stu[i].getKey()))
               { b++;}}
          if(b>=5){
              System.out.print("该卡已被锁定，无法操作");
          }
          else
      for(int i=0;i< 5;i++)
        {
          if(key.equals(stu[i].getKey()))
        {    
            while(k==1)
            {
            System.out.println();
            System.out.print("1.存款  2.取款  3.转账汇款  4.修改密码  5.查询余额  6.退卡");
            System.out.println();
            System.out.print("请选择：");
            num=scan1.nextInt();
            if(num==6)
            { System.out.println("卡已成功退出！请拿卡！");
                break;
            }
            switch(num)
            {
            case 1://存款
                double m;
                System.out.print("请输入存入的金额：");
                m=scan2.nextDouble();
                stu[i].cun(m);
                break;
            case 2://取款
                  int numm;
                    System.out.print("100元	500元	1000元	1500元	2000元	5000元	其他金额
"
                            + "1.退卡");
                    System.out.println();
                    System.out.print("请选择：");
                  numm=scan3.nextInt();
                  if(numm==1) break;
                  else
                stu[i].qu(numm);break;
            case 3://转账汇款
                String nummm;
                double cc;
                int n;
                System.out.print("请输入转账行号：");
                nummm=scan.nextLine();
                /*boolean b=true;
                for(int j=0;j<5;j++)
                    {if(!nummm.equals(stu[j].getNum()))
                    {
                        b=false;
                    }}
                if(b==false){
                    System.out.println("信息错误！");
                }*/
                for(int j=0;j<5;j++)
                if(nummm.equals(stu[j].getNum()))
                {
                    System.out.print("请输入转账金额：");
                    cc=scan.nextDouble();
                    System.out.print("请确认（1确认,0取消）");
                    n=scan.nextInt();
                    if(n==1)
                    {
                        stu[i].qu(cc);
                        stu[j].cun(cc);
                        System.out.print("转账成功!");
                    }
                    else if(n==0){
                        System.out.print("已取消！");
                    }
                    else{
                        System.out.print("发生错误！");
                    }
                }
                break;
            case 4:
                String kk;
                System.out.print("请输入修改的密码：");
                kk=scan.nextLine();
                stu[i].setKey(kk);
                break;
            case 5:
                System.out.print("余额为："+stu[i].getMoney());
                break;
            case 6:
                break;
            }
            }
        }}
     
    }
}

abstract class AccountY
{
    public abstract String getNum();
      public abstract void setKey(String s);
      public abstract String getKey();
      public abstract double getMoney();
      public abstract void cun(double m);
     public abstract void qu(double m);
}

class Account extends AccountY{
        private String num;//长度为11，由数字和字符组合
        private String name;//用户的姓名
        private String Date;//操作日期
        private String key;//账户密码
        private double money;//当前余额
    public Account(String n,String a,String b,String c,double d){num=n;name=a;Date=b;key=c;money=d;}
    public String getNum(){return num;}
    public String getName(){return name;}
      public String getDate(){return Date;}
      public void setKey(String s){
          key=s;
      }
      public String getKey(){return key;}
      public double getMoney(){return money;}
      public void cun(double m){
          if(m<=200000)
         money+=m;
          else
          {System.out.println("超出限额！");}
      }
     public void qu(double m){
         if(m<money)
        money-=m;
         else
             System.out.println("超出余额！");
      }
    }

二、实验结果截图

验证：

①TestInstanceof.java

代码

 public class TestInstanceof
{
    public static void main(String[] args) 
    {
        //声明hello时使用Object类，则hello的编译类型是Object，Object是所有类的父类
        //但hello变量的实际类型是String
        Object hello = "Hello";
        //String是Object类的子类，所以返回true。
        System.out.println("字符串是否是Object类的实例：" + (hello instanceof Object));
        //返回true。
        System.out.println("字符串是否是String类的实例：" + (hello instanceof String));
        //返回false。
        System.out.println("字符串是否是Math类的实例：" + (hello instanceof Math));
        //String实现了Comparable接口，所以返回true。
        System.out.println("字符串是否是Comparable接口的实例：" + (hello instanceof Comparable));
        String a = "Hello";
        //String类既不是Math类，也不是Math类的父类，所以下面代码编译无法通过
        //System.out.println("字符串是否是Math类的实例：" + (a instanceof Math));
    }
}

运行结果截图：

②TestCast.java

代码如下：

class Mammal{}
class Dog extends Mammal {}
class Cat extends Mammal{}

public class TestCast
{
    public static void main(String args[])
    {
        Mammal m;
        Dog d=new Dog();
        Cat c=new Cat();
        m=d;
        //d=m;
        d=(Dog)m;
        //d=c;
        //c=(Cat)m;

    }
}

运行结果没有出错！

③Zoo.java

代码如下：

package zoo4;

import java.util.Vector;

public class Zoo {

    public static void main(String args[]) {
        Feeder f = new Feeder("小李");
        Vector<Animal> ans = new Vector<Animal>();//可随时向其中加入或移除对象

        //饲养员小李喂养一只狮子
        ans.add(new Lion());
        //饲养员小李喂养十只猴子
        for (int i = 0; i < 10; i++) {
            ans.add(new Monkey());
        }
        //饲养员小李喂养5只鸽子
        for (int i = 0; i < 5; i++) {
            ans.add(new Pigeon());
        }
        f.feedAnimals(ans);
    }
}

class Feeder {

    public String name;

    Feeder(String name) {
        this.name = name;
    }

    public void feedAnimals(Vector<Animal> ans) {
        for (Animal an : ans) {
            an.eat();
        }
    }
}

abstract class Animal {

    public abstract void eat();
}

class Lion extends Animal {

    public void eat() {
        System.out.println("我不吃肉谁敢吃肉！");
    }
}

class Monkey extends Animal {

    public void eat() {
        System.out.println("我什么都吃，尤其喜欢香蕉。");
    }
}

class Pigeon extends Animal {

    public void eat() {
        System.out.println("我要减肥，所以每天只吃一点大米。");
    }
}

运行结果截图：