24.12.16
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；
3. 注意编程规范。
类图:
- 源代码
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;
}
public void deposit(double amount) {
state.deposit(amount);
System.out.println("现金余额为" + this.state.balance);
}
public void withdraw(double amount) {
state.withdraw(amount);
System.out.println("现金余额为" + state.balance);
}
}
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);
}
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;
System.out.println(balance);
stateCheck();
}
@Override
public void withdraw(double amount) {
balance -= amount;
stateCheck();
}
}
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！");
}
}
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();
}
}
public class Client {
public static void main(String[] args) {
Account acc = new Account("gazikel", 2500);
System.out.println("==========绿色状态存钱===========");
acc.deposit(1500);
System.out.println("------------------------------");
// 绿色状态取钱
System.out.println("==========绿色状态取钱===========");
acc.withdraw(4500);
System.out.println("------------------------------");
// 黄色状态存钱
System.out.println("==========黄色状态存钱===========");
acc.deposit(100);
System.out.println("------------------------------");
// 黄色状态取钱
System.out.println("==========黄色状态取钱===========");
acc.withdraw(700);
System.out.println("------------------------------");
// 红色状态取钱
System.out.println("==========红色状态取钱===========");
acc.withdraw(100);
// 红色状态存钱
System.out.println("==========红色状态存钱===========");
acc.deposit(1000);
}
}
}
