软件设计 石家庄铁道大学信息学院
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. 类图；
2. 源代码；
①、AccountState.java
package org.example.shiyanershier;
public abstract class AccountState {
protected Account acc;
protected double balance;
public abstract void stateCheck();
public abstract void deposit(double amount);
public abstract void withdraw(double amount);
}
②、GreenState.java
package org.example.shiyanershier;
public class GreenState extends AccountState {
public GreenState() {}
public GreenState(double amount, Account account) {
balance = amount;
acc = account;
}
@Override
public void stateCheck() {
if (balance >= 0) {
acc.setState(new GreenState(balance, acc));
System.out.println("当前为正常（绿色）状态");
} else if(balance <0 && balance >= -1000) {
acc.setState(new YellowState(balance, acc));
System.out.println("当前为欠费（黄色）状态");
} else {
acc.setState(new RedState(balance, acc));
System.out.println("当前透支（红色）状态");
}
}
@Override
public void deposit(double amount) {
balance += amount;
stateCheck();
}
@Override
public void withdraw(double amount) {
balance -= amount;
stateCheck();
}
}
③、RedState.java
package org.example.shiyanershier;
public class RedState extends AccountState {
public RedState(double amount, Account acc) {
this.balance = amount;
this.acc = acc;
}
@Override
public void stateCheck() {
if (balance >= 0) {
acc.setState(new GreenState(balance, acc));
System.out.println("当前为正常（绿色）状态");
} else if(balance <0 && balance >= -1000) {
acc.setState(new YellowState(balance, acc));
System.out.println("当前为欠费（黄色）状态");
} else {
acc.setState(new RedState(balance, acc));
System.out.println("当前透支（红色）状态");
}
}
@Override
public void deposit(double amount) {
balance += amount;
stateCheck();
}
@Override
public void withdraw(double amount) {
System.out.println("透支状态，无法取款！");
}
}
④、YellowState.java
package org.example.shiyanershier;
public class YellowState extends AccountState {
public YellowState(double amount, Account acc) {
this.balance = amount;
this.acc = acc;
}
@Override
public void stateCheck() {
if (balance >= 0) {
acc.setState(new GreenState(balance, acc));
System.out.println("当前为正常（绿色）状态");
} else if(balance <0 && balance >= -1000) {
acc.setState(new YellowState(balance, acc));
System.out.println("当前为欠费（黄色）状态");
} else {
acc.setState(new RedState(balance, acc));
System.out.println("当前透支（红色）状态");
}
}
@Override
public void deposit(double amount) {
balance += amount;
stateCheck();
}
@Override
public void withdraw(double amount) {
balance -= amount;
stateCheck();
}
}
⑤、Account.java
package org.example.shiyanershier;
public class Account {
private AccountState state;
private String owner;
public Account(String owner, double init) {
this.owner = owner;
state = new GreenState(init, this);
System.out.println("账户:" + this.owner + ",余额:" + init);
}
public void setState(AccountState state) {
this.state = state;
}
/**
* 存款
* @param amount
*/
public void deposit(double amount) {
state.deposit(amount);
System.out.println("现金余额为" + this.state.balance);
}
/**
* 取款
* @param amount
*/
public void withdraw(double amount){
state.withdraw(amount);
System.out.println("现金余额为" + state.balance);
}
}
⑥、Main.java
package org.example.shiyanershier;
public class Main {
public static void main(String[] args) {
Account acc = new Account("何不语", 2500);
acc.deposit(1000);
acc.deposit(2000);
acc.withdraw(5000);
acc.withdraw(7000);
acc.deposit(6000);
}
}
3. 运行结果。
