练习1：创建一个简单的银行程序包

package banking;

public class Account {

    private double balance;

    public Account(double balance)
    {
        this.balance=balance;
    }

    public double getBalance() {
        System.out.println("当前余额为："+balance+"元");
        return balance;
    }

    public double deposit(double add){
        balance+=add;
        System.out.println("存钱"+add+"元，当余额为"+balance+"元");
        return balance;
    }

    boolean    withdraw(double get){
        if(get<=balance)
        {
            System.out.println("取钱"+get+"元，当余额为"+balance+"元");
            return true;
        }
        else
        {
            System.out.println("‘余额不足");
            return false;
        }        

    }

}