C#

代码：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace 接口
{
    /// <summary>
    /// 接口：定义一个统一的标准
    /// 声明接口，接口中，只包含成员的生命，不包含任何的代码实现。
    /// 接口成员总是公有的，不添加也不需要添加public，也不能声明虚方法和虚静态方法
    /// </summary>
    interface IBankAccount
    {
        //方法
        void PayIn(decimal amount);

        //方法
        bool WithShowMyself(decimal amount);

        //属性
        decimal Balance { get; }
    }

    /// <summary>
    /// 继承自IBankAccount的接口
    /// </summary>
    interface ITransferBankAccount : IBankAccount
    {
        //转账          ：转入的目的地             ：转入金额
        bool TransferTo(IBankAccount destination, decimal amount);
    }

    class SaveAcount : IBankAccount
    {
        //私有变量
        private decimal banlance;

        //存款
        public void PayIn(decimal amount)
        {
            banlance += amount;
        }

        //取款
        public bool WithShowMyself(decimal amount)
        {
            if (banlance >= amount)
            {
                banlance -= amount;
                return true;
            }
            else
            {
                Console.WriteLine("余额不足！");
                return false;
            }
        }

        //账户余额
        public decimal Balance
        {
            get
            {
                return banlance;
            }
        }
    }

    //实现接口的类的相应成员必须添加public修饰
    class ITransferAccount : ITransferBankAccount
    {
        //私有变量
        private decimal banlance;

        //存款
        public void PayIn(decimal amount)
        {
            banlance += amount;
        }

        //取款
        public bool WithShowMyself(decimal amount)
        {
            if (banlance >= amount)
            {
                banlance -= amount;
                return true;
            }
            else
            {
                Console.WriteLine("余额不足！");
                return false;
            }
        }

        //账户余额
        public decimal Balance
        {
            get
            {
                return banlance;
            }
        }

        //转账
        public bool TransferTo(IBankAccount destination, decimal amount)
        {
            bool result = WithShowMyself(amount);

            if (result == true)
            {
                destination.PayIn(amount);
            }

            return result;
        }
    }


    class Program
    {
        static void Main(string[] args)
        {
            IBankAccount MyAccount = new SaveAcount();

            ITransferAccount YourAccount = new ITransferAccount();

            MyAccount.PayIn(10000);

            YourAccount.PayIn(30000);

            YourAccount.TransferTo(MyAccount, 5000);

            Console.WriteLine(MyAccount.Balance);//15000
            Console.WriteLine();
            Console.WriteLine(YourAccount.Balance);//25000

            Console.ReadKey();
        }
    }
}