java - 如何获取用户选择的类(class)？

Question

我读过一些关于它的帖子，但不确定其中是否是我一直在寻找的答案。我想通过用户输入选择一个类并检查它是否在列表中。我不想创建 if、switch 或 Map(我将使用很多类)。如果可能的话，我正在尝试用几行代码来完成此操作。谢谢!

public boolean isClassDefined(ArrayList<GeometricObject> geoObjects) {
    Class<?> classDefinedByUser=null;
    try {
        classDefinedByUser = Class.forName("Square");
        //as if user has typed "Square", being "class Square extends GeometricObject"
    } catch (ClassNotFoundException ex) {
        Logger.getLogger(Mission.class.getName()).log(Level.SEVERE, null, ex);
    }

    for (GeometricObject geo : geoObjects) {
        //here is where i don't know what to do
        //I want to create a if to check if there is an object (of the class
        //defined by the user) initialized into ArrayList "geoObjects"
        //I don't want to use lots of ifs
        if (geo instanceof classDefinedByUser.getClass()) {
            //if exists a Square type object, return true
            return true;
        }
    }
    return false;
}

Answer 1

使用Class.isInstance检查您拥有的对象是否是类的实例。

您的支票应该是:

if(classDefinedByUser.isInstance(geo))

请注意，如果geo == null，此方法将返回false(即使它应该是该类的实例)