实验题目
修改 Bank 类来实现单子设计模式：
实验目的
单子模式。
提示
- 修改 Bank 类，创建名为 getBank 的公有静态方法，它返回一个 Bank 类的实例。
- 单个的实例应是静态属性，且为私有。同样，Bank 构造器也应该是私有的。
创建 CustomerReport 类
- 在前面的银行项目练习中，“客户报告”嵌入在 TestBanking 应用程序的 main 方法中。在这个练习中，将该部分代码被改为放在banking.reports 包的 CustomerReport 类中。您的任务是修改这个类，使其使用单一银行对象。
- 查找标注为注释块/** * ***/的代码行.修改该行以检索单子银行对象。
编译并运行 TestBanking 应用程序 看到下列输入结果：
CUSTOMERS REPORT
================
Customer: Simms, Jane
Savings Account: current balance is ￥500.0
Checking Account: current balance is ￥200.0
Customer: Bryant, Owen
Checking Account: current balance is ￥200.0
Customer: Soley, Tim
Savings Account: current balance is ￥1500.0
Checking Account: current balance is ￥200.0
Customer: Soley, Maria
Checking Account: current balance is ￥200.0
Savings Account: current balance is ￥150.0代码
【Account.java】类
package banking;
public class Account {
protected double balance; //银行帐户的当前（或即时）余额
//公有构造器 ，这个参数为 balance 属性赋值
public Account(double init_balance) {
this.balance = init_balance;
}
//用于获取经常余额
public double getBalance() {
return balance;
}
/**
* 向当前余额增加金额
* @param amt 增加金额
* @return 返回 true（意味所有存款是成功的）
*/
public boolean deposit(double amt){
balance+=amt;
return true;
}
/**
* 从当前余额中减去金额
* @param amt 提款数目
* @return 如果 amt小于 balance, 则从余额中扣除提款数目并返回 true，否则余额不变返回 false。
*/
public boolean withdraw(double amt){
if (amt < balance){
balance-=amt;
return true;
}else{
return false;
}
}
}【Customer.java】类
package banking;
public class Customer {
private String firstName;
private String lastName;
private Account[] accounts = new Account[10];
private int numOfAccounts;
public Customer(String f, String l) {
this.firstName = f;
this.lastName = l;
}
public String getFirstName() {
return firstName;
}
public String getLastName() {
return lastName;
}
/**
* 通过下标索引获取 account
* @param index 下标索引
* @return account
*/
public Account getAccount(int index) {
return accounts[index];
}
/**
* 获取 numOfAccounts
* @return numOfAccounts
*/
public int getNumOfAccounts() {
return numOfAccounts;
}
/**
* 添加 account，并将 numOfAccounts+1
* @param acct account
*/
public void addAccount(Account acct) {
accounts[numOfAccounts++]=acct;
}
}【Bank.java】类
package banking;
/**
* 银行类
*/
public class Bank {
private Customer[] customers; //Customer对象的数组
private int numberOfCustomer; //整数，跟踪下一个 customers 数组索引
private static Bank bankInstance = null;
/**
* getBanking 的公有静态方法，它返回一个 Bank 类的实例。
* @return 返回一个 Bank 类的实例。
*/
public static Bank getBank(){
if(bankInstance==null){
bankInstance = new Bank();
}
return bankInstance;
}
/**
* 单例模式中构造器也应该是私有的，以合适的最大尺寸（至少大于 5）初始化 customers 数组。
*/
private Bank() {
customers = new Customer[10];
}
/**
* 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 customer 数组中。还必须把 numberOfCustomers 属性的值加 1。
* @param f 姓
* @param l 名
*/
public void addCustomer(String f,String l){
customers[numberOfCustomer++]=new Customer(f,l);
}
/**
* 通过下标索引获取 customer
* @param index 下标索引
* @return customer
*/
public Customer getCustomer(int index) {
return customers[index];
}
public int getNumOfCustomers() {
return numberOfCustomer;
}
}【CheckingAccount.java】类
package banking;
public class CheckingAccount extends Account{
private double overdraftProtection;
public CheckingAccount(double balance) {
super(balance);
}
public CheckingAccount(double balance, double protect) {
super(balance);
this.overdraftProtection = protect;
}
/**
* 此方法必须执行下列检查。如 果当前余额足够弥补取款 amount,则正常进行。
* 如果不够弥补但是存在透支保护，则尝试用 overdraftProtection 得值来弥补该差值（balance-amount）.
* 如果弥补该透支所需要的金额大于当前的保护级别。则整个交易失败，但余额未受影响。
* @param amt 提款数目
* @return 返回true代表交易成功，否则交易失败
*/
@Override
public boolean withdraw(double amt){
if (balance < amt){
if (amt-balance>overdraftProtection) {
return false;
}else {
overdraftProtection-=amt-balance;
balance=0;
return true;
}
}else {
balance-=amt;
return true;
}
}
}【SavingsAccount.java】类
package banking;
public class SavingsAccount extends Account{
private double interestRate;
public SavingsAccount(double balance, double interest_Rate) {
super(balance);
this.interestRate = interest_Rate;
}
}【CustomerReport.java】类
package banking.reports;
import banking.Account;
import banking.Bank;
import banking.Customer;
import banking.SavingsAccount;
public class CustomerReport {
/**
* 生成客户报告，Generate a report
*/
public static void generalReport() {
Bank bank = Bank.getBank();
System.out.println("\t\t\tCUSTOMERS REPORT");
System.out.println("\t\t\t================");
for (int cust_idx = 0; cust_idx < bank.getNumOfCustomers(); cust_idx++) {
Customer customer = bank.getCustomer(cust_idx);
System.out.println();
System.out.println("Customer: "
+ customer.getLastName() + ", "
+ customer.getFirstName());
for (int acct_idx = 0; acct_idx < customer.getNumOfAccounts(); acct_idx++) {
Account account = customer.getAccount(acct_idx);
String account_type = "";
// Determine the account type
/*** Step 1:
**** Use the instanceof operator to test what type of account
**** we have and set account_type to an appropriate value, such
**** as "Savings Account" or "Checking Account".
***/
if (account instanceof SavingsAccount) {
account_type = "Savings Account";
} else {
account_type = "Checking Account";
}
// Print the current balance of the account
/*** Step 2:
**** Print out the type of account and the balance.
**** Feel free to use the currency_format formatter
**** to generate a "currency string" for the balance.
***/
System.out.println("\t" + account_type + ": current balance is ￥" + account.getBalance());
}
}
}
}【TestBanking.java】类
package banking;/*
* This class creates the program to test the banking classes.
* It creates a set of customers, with a few accounts each,
* and generates a report of current account balances.
*/
import banking.reports.CustomerReport;
import java.text.NumberFormat;
public class TestBanking {
public static void main(String[] args) {
NumberFormat currency_format = NumberFormat.getCurrencyInstance();
Bank bank = Bank.getBank();
Customer customer;
// Create several customers and their accounts
bank.addCustomer("Jane", "Simms");
customer = bank.getCustomer(0);
customer.addAccount(new SavingsAccount(500.00, 0.05));
customer.addAccount(new CheckingAccount(200.00, 400.00));
bank.addCustomer("Owen", "Bryant");
customer = bank.getCustomer(1);
customer.addAccount(new CheckingAccount(200.00));
bank.addCustomer("Tim", "Soley");
customer = bank.getCustomer(2);
customer.addAccount(new SavingsAccount(1500.00, 0.05));
customer.addAccount(new CheckingAccount(200.00));
bank.addCustomer("Maria", "Soley");
customer = bank.getCustomer(3);
// Maria and Tim have a shared checking account
customer.addAccount(bank.getCustomer(2).getAccount(1));
customer.addAccount(new SavingsAccount(150.00, 0.05));
CustomerReport.generalReport();
}
}
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