练习目标－使用有返回值的方法：在本练习里，将修改withdraw方法以返回一个布尔值来指示交易是否成功。
任务
1．修改Account类
a.修改deposit 方法返回true（意味所有存款是成功的）。
b.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exercise2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
//Account类
package banking;
public class Account {
private double balance;
public Account(double i)
{
balance=i;
}
public double getBalance()
{
return balance;
}
public boolean deposit(double i)
{
balance+=i;
System.out.print("Deposit "+i);
return true;
}
public boolean withdraw(double i)
{
if(balance>=i)
{
balance-=i;
System.out.print("Withdraw "+i);
return true;
}
else
{
System.out.print("余额不足");
return false;
}
}
}
//Testbanking类
package banking;
public class TestBanking {
public static void main(String[] args) {
Account a=new Account(500.00);
System.out.println("Creating an account with a "+a.getBalance()+"balance");
a.withdraw(150.00);
a.deposit(22.50);
a.withdraw(47.62);
System.out.println("The account has a balance of "+a.getBalance());
Customer c=new Customer("Jane", "Smith");
Account b=new Account(500.00);
c.setAccount(b);
a=c.getAccount();
System.out.println("Creating her account with a "+a.getBalance()+"balance");
System.out.println(":"+a.withdraw(150.00));
System.out.println(":"+a.deposit(22.50));
System.out.println(":"+a.withdraw(47.62));
System.out.println("Customer ["+c.getFirstName()+","+c.getLastName()+"] has a balance of "+a.getBalance());
}
}
//运行
Creating an account with a 500.0balance
Withdraw 150.0Deposit 22.5Withdraw 47.62The account has a balance of 324.88
Creating the customer Jane Smith
Creating her account with a 500.0balance
Withdraw 150.0:true
Deposit 22.5:true
Withdraw 47.62:true
Customer [Jane,Smith] has a balance of 324.88