用List表示多重性

练习目标－在类中使用List作为模拟集合操作： 在本练习中，将用List实现银行与客户间的多重关系。

任务

对银行来说，可添加Bank类。 Bank 对象跟踪自身与其客户间的关系。用Customer对象的List实现这个集合化的关系。还要保持一个整数属性来跟踪银行当前有多少客户。

                      

1. 创建 Bank 类

1. 为Bank类增加两个属性：customers(Customer对象的List)和numberOfCustomers(整数， 当前Customer对象的数量)

1. 添加公有构造器，初始化customersList。

1. 添加addCustomer方法。该方法必须依照参数（姓，名）构造一个新的Customer对象然后把它放到customerList中。

1. 添加getNumOfCustomers 访问方法，它返回numberofCustomers属性值。

1. 添加getCustomer方法。它返回与给出的index参数相关的客户。

1. 编译并运行TestBanking程序。可以看到下列输出结果：

Customer 1 is Simms,Jane

Customer 2 is Bryant,Owen

   Customer 3 is Soley,Tim

   Customer 4 is Soley,Maria

当前客户数量 = 4

package banking;

import java.util.ArrayList;
import java.util.List;

public class Bank1 
{
    private  List<Customer> customers ;
    private int numberOfCustomers = 1 ;
    
    public Bank1( )
    {
        customers =new ArrayList<>() ;
    }
    
    public void addCustomer(String firstName ,String lastName)
    {
        customers.add(new Customer(firstName,lastName));
    }

    public int getNumberOfCustomers() {
        numberOfCustomers=customers.size();
        return numberOfCustomers;
    }

     public  Customer getCustomer(int index)
     {
            Customer s=new Customer();
            s=customers.get(index); 
            return s;
        }



    
    
    
    
    
}

package banking;

import java.util.List;

public class Customer extends Account
{
    //成员属性
    private String firstName ;
    private String lastName ;
    private double account ;
    
    //构造方法
    public Customer() 
    {
    
    }
    //构造方法
    public Customer(String f , String l) 
    {
        this.firstName = f ;
        this.lastName = l ;
    }
    
    //get set 
    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public double getAccount() {
        return account;
    }

    public void setAccount(double account) {
        this.account = account;
    }
    
    public String toString() {
        return  firstName + ", " + lastName ;
    }

    
}

package banking;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

public class TestBanking {

    public static void main(String[] args) 
    {
        //实例化账户
        Account at = new Account(500) ;
        
        System.out.println("Creating an account with a  "+at.getBalance( ) +" balance") ;
        System.out.println("Withdraw "+(at.getBalance( ) -at.withdraw(150) ));
        double x=at.getBalance( );
        System.out.println("Deposit "+(at.deposit(22.5)-x)) ;
        System.out.println("Withdraw "+(at.getBalance( ) -at.withdraw(47.62) ));
        System.out.println("The account has a balance of "+at.getBalance()) ;
        
        System.out.println("————————————————————————");
        
        //实例化顾客
        Customer cr = new Customer( ) ;
    
        cr.setFirstName("Jane");
        cr.setLastName("Smith");
        cr.setBalance(500);
        System.out.println("Creating the customer "+cr.getFirstName() +" "+cr.getLastName());
        System.out.println("Creating her account  with  a " +cr.getBalance()+" balance");
        System.out.println("Withdraw "+(cr.getBalance()-cr.withdraw(150)) );
        double x1 = cr.getBalance( ) ;
        System.out.println("Deposit "+(cr.deposit(22.5)-x1));
        System.out.println("Withdraw "+(cr.getBalance()-cr.withdraw(47.62)));
        System.out.println("Customer "+cr.getLastName()+" "+cr.getFirstName()+
                                    " has a balance of "+cr.getBalance());
    
        System.out.println("————————————————————————");
        
        Customer cr1 = new Customer( ) ;
        
        cr1.setFirstName("Jane");
        cr1.setLastName("Smith");
        cr1.setBalance(500);
        System.out.println("Creating the customer "+cr1.getFirstName() +" "+cr1.getLastName());
        System.out.println("Creating her account  with  a " +cr1.getBalance()+" balance");
        System.out.println(cr1.withdraw1(150) );
        System.out.println(cr1.deposit1(22.5));
        System.out.println(cr1.withdraw1(47.62));
        System.out.println(cr1.withdraw1(400));
        System.out.println("Customer "+cr1.getLastName()+" "+cr1.getFirstName()+
                                            " has a balance of "+cr1.getBalance());
        
        System.out.println("————————————————————————");
        
        Bank bk =new Bank( ) ;
                
        bk.addCustomer( "Simms" , "Jane" );
        bk.addCustomer( "Bryant" , "Owen" );
        bk.addCustomer( "Soley" , "Tim" );
        bk.addCustomer( "Soley" , "Maria" );
    
        System.out.println("————————————————————————");
        
//
        
        Bank1 bk1 = new Bank1(){};
        
        bk1.addCustomer("Simms", "Jane");
        bk1.addCustomer("Bryant", "Owen");
        bk1.addCustomer("Soley","Tim");
        bk1.addCustomer("Soley","Maria");
        
        for(int i=0 ;i <bk1.getNumberOfCustomers();i++)
        {
            System.out.println("Customer "+(i+1)+" is"+" "+bk1.getCustomer(i));
        }
        
        System.out.println("当前客户数量 = "+bk1.getNumberOfCustomers());
        
        System.out.println("————————————————————————");
    }

}