具体代码

//Account.java
package org.example.test020;

public class Account {
    public AccountState getAccountState() {
        return accountState;
    }

    public void setAccountState(AccountState accountState) {
        this.accountState = accountState;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    private AccountState accountState;
    private String name;

    public Account(String name) {
        this.name = name;
        this.accountState = new GreenState(this);
        System.out.println(name + "开户成功！初始金额：0元");
        System.out.println("---------------------------------");
    }

    public void inMoney(double money) {
        accountState.inMoney(money);
    }

    public void outMoney(double money) {
        accountState.outMoney(money);
    }


}

//AccountState.java
package org.example.test020;

public abstract class AccountState {
    public Account getAccount() {
        return account;
    }

    public void setAccount(Account account) {
        this.account = account;
    }

    public double getMmm() {
        return mmm;
    }

    public void setMmm(double mmm) {
        this.mmm = mmm;
    }

    public String getStateName() {
        return stateName;
    }

    public void setStateName(String stateName) {
        this.stateName = stateName;
    }

    protected Account account;
    protected double mmm;//余额的计算
    protected String stateName;
    public abstract void checkMoney(double money);

    public void inMoney(double money) {
        System.out.println(account.getName() + "存款" + money + "元");
        this.mmm += money;
        checkMoney(mmm);
        System.out.println("当前余额为：" + this.mmm);
        System.out.println("当前状态为：" + account.getAccountState().stateName);
    }

    public void outMoney(double money) {
        System.out.println(account.getName() + "取款" + money + "元");
        this.mmm -= money;
        checkMoney(mmm);
        System.out.println("当前余额为：" + this.mmm);
        System.out.println("当前状态为：" + account.getAccountState().stateName);
    }
}

//GreenState.java
package org.example.test020;

public class GreenState extends AccountState {
    public GreenState(AccountState accountState) {
        this.account = accountState.account;
        this.mmm = accountState.mmm;
        this.stateName = "正常状态";
    }

    public GreenState(Account account) {
        this.mmm = 0;
        this.account = account;
        this.stateName = "正常状态";
    }
    @Override
        public void checkMoney(double money) {
        if (money <= -1000) {
            account.setAccountState(new RedState(this));
        }
        else if (money >= -1000 && money < 0) {
            account.setAccountState(new YellowState(this));
        }
    }
}

//RedState.java
package org.example.test020;

public class RedState extends AccountState {

    public RedState(AccountState accountState) {
        this.account = accountState.account;
        this.mmm = accountState.getMmm();
        this.stateName = "透支状态";
    }
    @Override
        public void checkMoney(double money) {
        if (money >= 0) {
            account.setAccountState(new GreenState(this));
        }
        else if (money >= -1000 && money < 0) {
            account.setAccountState(new YellowState(this));
        }
    }

    public void outMoney(double m1) {
        System.out.println("对不起!" + account.getName() + "不能取款！");
        System.out.println("当前余额：" + mmm + ",当前状态为：" + account.getAccountState().stateName);
    }
}

//YellowState.java
package org.example.test020;

public class YellowState extends AccountState {

    public YellowState(AccountState accountState) {
        this.account = accountState.account;
        this.mmm = accountState.getMmm();
        this.stateName = "欠费状态";
    }
    @Override
        public void checkMoney(double money) {
        if (money >= 0) {
            account.setAccountState(new GreenState(this));
        }
        else if (money <= -1000) {
            account.setAccountState(new RedState(this));
        }
    }
}

//Main.java
package org.example.test020;

public class Main {
    public static void main(String[] args) {
        Account account = new Account("张三");

        account.inMoney(2000);
        System.out.println("----------------");
        account.outMoney(1000);
        System.out.println("----------------");
        account.outMoney(1500);
        System.out.println("----------------");
        account.outMoney(1000);
        System.out.println("----------------");
        account.outMoney(500);
    }
}