Java - SubType枚举或子类 [英] Java - SubType Enums or SubClass

问题描述

我试图将一个枚举对应于一个类或返回该类，但我得到解决。如果我使用 CommandType.SELLSHARES 来返回 SellShares.class ，这种行为是否可行？或者我可以使用继承自父类型的不同类别来组织枚举？

I'm trying to have an enum correspond to a class or return that class but I get to resolve. Is this behavior possible if I use the CommandType.SELLSHARES for it to return SellShares.class? Or can I organize the enums with different categories that inherit from the parent type?

命令 - ADMIN ， USER ，客户端

public enum CommandType {

// SELLSHARES, BUYSHARES, UPDATEUSER, ADDUSER, ADMINASSIGNMENT, BANUSER, CHANGESTATUS, REMOVEUSER

    SELLSHARES (SellShares.class),
    BUYSHARES (BuyShares.class);

    private Class<Command> command;

    CommandType(Class<Command> command) {
        this.command = command;
    }

    private Class<Command> command() { return command; }

    public static <T extends Enum<T>> T getInstance(final String value,
            final Class<T> enumClass) {
        return Enum.valueOf(enumClass, value);
    }

}

或

public enum CommandType {
    AdminCommands,
    UserCommands
}

enum AdminCommands {
    UPDATEUSER,
    ADDUSER,
    ADMINASSIGNMENT,
    BANUSER,
    CHANGESTATUS,
    REMOVEUSER
}

enum User {
    SELLSHARES,
    BUYSHARES
}

有问题 getByType

void initialCommands() throws Exception
    {
        listCommands = Commands.getByType(Commands.Type.ADMIN);

        for (Commands command : listCommands)
            {
                Command commandss = command.newInstance();
                //addCommand(command.getCommand());
                //log.trace(command.newInstance());

            }

    }

推荐答案

你必须寻找这样的东西：

You must be looking for something like this:

public enum Commands {

    UPDATE_USER(Type.ADMIN, UpdateUser.class),
    ADD_USER(Type.ADMIN, AddUser.class),
    ADMIN_ASSIGNMENT(Type.ADMIN, AdminAssignment.class),
    BAN_USER(Type.ADMIN, BanUser.class),
    CHANGE_STATUS(Type.ADMIN, ChangeStatus.class),
    REMOVE_USER(Type.ADMIN, RemoveUser.class),

    SELL_SHARES(Type.USER, SellShares.class),
    BUY_SHARES(Type.USER, BuyShares.class);

    public enum Type {
        ADMIN,
        USER;
    }

    public static List<Commands> getByType(Type type) {
        List<Commands> commands = new ArrayList<Commands>();
        for (Commands command : values()) {
            if (command.type.equals(type)) {
                commands.add(command);
            }
        }
        return commands;
    }

    private final Type type;

    private final Class<? extends Command> command;

    private Commands(Type type, Class<? extends Command> command) {
        this.type = type;
        this.command = command;
    }

    public Class<? extends Command> getCommand() {
        return command;
    }

    public Command newInstance() throws Exception {
        return command.newInstance();
    }

}

要创建一个实例，只需使用：

To create an instance, simply use:

Commands.UPDATE_USER.newInstance();

获取给定类型的所有命令：

To get all the commands for a given type:

Commands.getByType(Commands.Type.ADMIN);

请注意，使用此方法，命令子类必须实现公共空白构造函数。

Note that using this method, the Commands subclasses must implement a public nullary constructor.

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