英文:
Java: instanceof doesn't compile
问题
I'm a newbie to Java and want to write a method checking if this object is of a sub class of given class <p_SuperClassName>.
Eclipse denies compilation of the following code giving the message that "cls_Super can not be resolved to a type". I don't know why. Do you have a quick answer to this? Thx a lot in advance!
protected boolean isOfSubClassOf(String p_SuperClassName) {
boolean res = false;
Class<?> cls_Super = null;
try {
cls_Super = Class.forName(p_SuperClassName);
res = (this instanceof cls_Super);
} catch (ClassNotFoundException cnfe) {
System.out.println("ClassNotFoundException: Did not find class '" + p_SuperClassName + "'.");
cnfe.printStackTrace();
}
return res;
}
如前所述。
英文:
I'm a newbie to Java and want to write a method checking if this object is of a sub class of given class <p_SuperClassName>.
Eclipse denies compilation of the following code giving the message that "cls_Super can not be resolved to a type". I don't know why. Do you have a quick answer to this? Thx a lot in advance!
protected boolean isOfSubClassOf(String p_SuperClassName) {
boolean res = false;
Class<?> cls_Super = null;
try {
cls_Super = Class.forName(p_SuperClassName);
res = (this instanceof cls_Super);
} catch (ClassNotFoundException cnfe) {
System.out.println("ClassNotFoundException: Did not find class '" + p_SuperClassName + "'.");
cnfe.printStackTrace();
}
return res;
}
as described previously
答案1
得分: 2
无法使用instanceof关键字来检查类变量，只能使用文字类型名称（例如obj instanceof ActualSuperClassName）。使用类型为Class的实例（例如您的示例中的cls_Super），可以通过使用Class.isInstance方法执行相同的测试，如下所示：
res = cls_Super.isInstance(this);
英文:
You can't use a Class variable with the instanceof keyword, only the literal type name (e.g. obj instanceof ActualSuperClassName). With an instance of type Class (i.e. cls_Super, in your example), you can perform the same test by using the Class.isInstance method, i.e.:
res = cls_Super.isInstance(this);
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