12.22

 

 

实验 22：状态模式

本次实验属于模仿型实验，通过本次实验学生将掌握以下内容： 

1、理解状态模式的动机，掌握该模式的结构；

2、能够利用状态模式解决实际问题。

 

[实验任务一]：银行账户

用Java代码模拟实现课堂上的“银行账户”的实例，要求编写客户端测试代码模拟用户存款和取款，注意账户对象状态和行为的变化。

实验要求：

1. 画出对应的类图；

 

2. 提交源代码；

package org.test22;

 

import javafx.scene.media.AudioClip;

 

public class BankAccount{

    private State state;

 

    public BankAccount(State state) {

        this.state = state;

    }

 

    public void deposit(double amount) {

        state.deposit(amount);

    }

 

    public void withdraw(double amount) {

        if (state instanceof OpenState) {

            state.withdraw(amount);

        } else {

            System.out.println("账户已关闭，不能取款");

        }

    }

 

    public State getState() {

        return this.state;

    }

}

 

 

 

package org.test22;

 

public class Client {

    public static void main(String[] args) {

        OpenState openState = new OpenState();

        ClosedState closedState = new ClosedState();

        BankAccount openAccount = new BankAccount(openState);

        openAccount.deposit(500); // 存款 500 元

        openAccount.withdraw(200); // 取款 200 元，余额不足，不能取款

        openAccount.withdraw(500); // 取款 500 元，成功取出 300 元，余额为 500 - 300 = 200 元

        System.out.println("当前账户余额：" + openAccount.getState().getBalance());

        closedState.deposit(5000);

    }

}

 

 

 

 

 

package org.test22;

 

public class ClosedState extends State{

    private double balance=0;

    @Override

    public void deposit(double amount) {

 

        System.out.println("账户已关闭，不能存款");

    }

 

    @Override

    public void withdraw(double amount) {

        System.out.println("账户已关闭，不能取款");

    }

 

    @Override

    public double getBalance() {

        return this.balance;

    }

}

 

 

 

 

 

package org.test22;

 

public class OpenState extends State{

    private double balance=0;

    @Override

    public void deposit(double amount) {

        System.out.println("存款成功，存款金额：" + amount);

        balance+=amount;

    }

 

    @Override

    public void withdraw(double amount) {

        if (balance-amount>=0) {

            System.out.println("取款成功，取款金额：" + amount);

            balance-=amount;

 

        } else {

            System.out.println("余额不足，不能取款");

        }

    }

 

    @Override

    public double getBalance() {

        return this.balance;

    }

}

 

 

package org.test22;

 

public abstract class State {

    public abstract void deposit(double amount);

    public abstract void withdraw(double amount);

    public abstract double getBalance();

}

3. 注意编程规范。