classcastexception

问题 I am doing a JBoss SEAM project and when I view a form I get this error. java.lang.ClassCastException: it.cogitoweb.csi.entity.csiorelav.CsiTipoLav cannot be cast to it.cogitoweb.csi.entity.csiorelav.CsiTipoLav Its alway the same JPA class which is related to the form which is shown on the screen, it doesn\'t make sense to me why is it the same class, it seems impossible. 回答1: This happens when two different ClassLoader objects load classes with the same name. The equality of two classes in

问题 The following code (run in android) always gives me a ClassCastException in the 3rd line: final String[] v1 = i18nCategory.translation.get(id); final ArrayList<String> v2 = new ArrayList<String>(Arrays.asList(v1)); String[] v3 = (String[])v2.toArray(); It happens also when v2 is Object[0] and also when there are Strings in it. Any Idea why? 回答1: This is because when you use toArray() it returns an Object[], which can't be cast to a String[] (even tho the contents are Strings) This is because

问题 public class Animal { public void eat() {} } public class Dog extends Animal { public void eat() {} public void main(String[] args) { Animal animal = new Animal(); Dog dog = (Dog) animal; } } The assignment Dog dog = (Dog) animal; does not generate a compilation error, but at runtime it generates a ClassCastException . Why can\'t the compiler detect this error? 回答1: By using a cast you're essentially telling the compiler "trust me. I'm a professional, I know what I'm doing and I know that

问题 I read some articles written on \"ClassCastException\", but I couldn\'t get a good idea on that. Is there a good article or what would be a brief explanation? 回答1: Straight from the API Specifications for the ClassCastException: Thrown to indicate that the code has attempted to cast an object to a subclass of which it is not an instance. So, for example, when one tries to cast an Integer to a String , String is not an subclass of Integer , so a ClassCastException will be thrown. Object i =

问题 I have 2 different Java projects, one has 2 classes: dynamicbeans.DynamicBean2 and dynamic.Validator . On the other project, I load both of these classes dynamically and store them on an Object class Form { Class beanClass; Class validatorClass; Validator validator; } I then go ahead and create a Validator object using validatorClass.newInstance() and store it on validator then I create a bean object as well using beanClass.newInstance() and add it to the session. portletRequest.setAttribute(