实验题目

修改 withdraw 方法以返回一个布尔值，指示交易是否成功。

实验目的

使用有返回值的方法。

提示

1. 修改 Account 类

   

   1. 修改 deposit 方法返回 true（意味所有存款是成功的）。
   2. 修改 withdraw 方法来检查提款数目是否大于余额。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。

2. 在 exercise3 主目录编译并运行 TestBanking 程序，将看到下列输出：

   Creating the customer Jane Smith.
   Creating her account with a 500.00 balance.
   Withdraw 150.00: true
   Deposit 22.50: true
   Withdraw 47.62: true
   Withdraw 400.00: false
   Customer [Smith, Jane] has a balance of 324.88
   

代码

【Account.java】类

package banking;

public class Account {

    private 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 account;

    public Customer(String f, String l) {
        this.firstName = f;
        this.lastName = l;
    }

    public String getFirstName() {
        return firstName;
    }

    public String getLastName() {
        return lastName;
    }

    public Account getAccount() {
        return account;
    }

    public void setAccount(Account acct) {
        this.account = acct;
    }
}

【TestBanking.java】类

package banking;/*
 * This class creates the program to test the banking classes.
 * It creates a new Bank, sets the Customer (with an initial balance),
 * and performs a series of transactions with the Account object.
 */

import banking.*;

public class TestBanking {

  public static void main(String[] args) {
    Customer customer;
    Account  account;

    // Create an account that can has a 500.00 balance.
    System.out.println("Creating the customer Jane Smith.");
	//code
    customer = new Customer("Jane","Smith");
    System.out.println("Creating her account with a 500.00 balance.");
	//code
    account = new Account(500.00);
    customer.setAccount(account);

    // Perform some account transactions
    System.out.println("Withdraw 150.00: " + account.withdraw(150.00));
    System.out.println("Deposit 22.50: " + account.deposit(22.50));
    System.out.println("Withdraw 47.62: " + account.withdraw(47.62));
    System.out.println("Withdraw 400.00: " + account.withdraw(400.00));

    // Print out the final account balance
    System.out.println("Customer [" + customer.getLastName()
		       + ", " + customer.getFirstName()
		       + "] has a balance of " + account.getBalance());
  }
}