java防止了很多if并用设计模式替换它

Question

我在我的应用程序中使用此代码,我发现它非常难看.这样做有一种聪明的方法吗？

for (final ApplicationCategories applicationCategorie : applicationCategories) {
          if (applicationCategorie == ApplicationCategories.PROJECTS) {
              // invoke right method
            } else if (applicationCategorie == ApplicationCategories.CALENDAR) {
              // ...
            } else if (applicationCategorie == ApplicationCategories.COMMUNICATION) {

            } else if (applicationCategorie == ApplicationCategories.CONTACTS) {

            } else if (applicationCategorie == ApplicationCategories.DOCUMENTS) {

            } else if (applicationCategorie == ApplicationCategories.WORKINGBOOK) {

            }
        }

我的目标是处理包含在枚举列表中的所有应用程序类别枚举.

Answer 1

您可以做的最少是声明处理依赖于enum内部的行为的方法ApplicationCategories.这样,如果要为枚举添加新值,则只需更改相对于枚举的代码.

通过这种方式,您的代码遵循开放封闭原则,因此更易于维护.

enum ApplicationCategories {
    PROJECTS,
    CALENDAR,
    // And so on...
    WORKINGBOOK;

    public static void handle(ApplicationCategories category) {
        switch (category) {
            case PROJECTS:
                // Code to handle projects
                break;
            case CALENDAR:
                // Code to handle calendar
                break;
            // And so on
        }
    }
}

只有在您不需要任何外部信息来处理枚举值时,此解决方案才可行.

请记住,您还可以向枚举值添加字段.

编辑

如果需要,您还可以实施策略设计模式.首先,定义策略接口和一些具体实现.

interface CategoryStrategy {
    void handle(/* Some useful input*/);
}
class ProjectStrategy implements Strategy {
    public void handle(/* Some useful input*/) {
        // Do something related to projects...
    }
}
class CalendarStrategy implements Strategy {
    public void handle(/* Some useful input*/) {
        // Do something related to calendars...
    }
}
//...

然后,您可以修改枚举以使用上述策略.

enum ApplicationCategories {
    PROJECTS(new ProjectStrategy()),
    CALENDAR(new CalendarStrategy()),
    // And so on...
    WORKINGBOOK(new WorkingBookStrategy());

    private CategoryStrategy strategy;
    ApplicationCategories(CategoryStrategy strategy) {
        this.strategy = strategy;
    }

    public static void handle(ApplicationCategories category) {
        category.strategy.handle(/* Some inputs */);
    }
}

显然,上面的代码只是一个草图.