在 Java 中为状态更改实现撤消

// 定义命令接口
interface Command {
    void execute();
    void undo();
}

// 具体命令实现
class ConcreteCommand implements Command {
    private Receiver receiver;
    private String oldState;
    private String newState;

    public ConcreteCommand(Receiver receiver, String oldState, String newState) {
        this.receiver = receiver;
        this.oldState = oldState;
        this.newState = newState;
    }

    @Override
    public void execute() {
        receiver.changeState(oldState, newState);
    }

    @Override
    public void undo() {
        receiver.changeState(newState, oldState);
    }
}

// 接收者
class Receiver {
    private String state;

    public void changeState(String oldState, String newState) {
        if (this.state.equals(oldState)) {
            this.state = newState;
            System.out.println("状态已更改为：" + newState);
        } else {
            System.out.println("状态更改失败，当前状态为：" + this.state);
        }
    }
}

// 客户端代码
public class Client {
    public static void main(String[] args) {
        Receiver receiver = new Receiver();
        Command command = new ConcreteCommand(receiver, "状态1", "状态2");

        // 执行操作
        command.execute();

        // 撤销操作
        command.undo();
    }
}