java.lang.ClassCastException: java.util.ArrayList 不能转换为 antlr.collections.List
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java.lang.ClassCastException: java.util.ArrayList cannot be cast to antlr.collections.List
提问by Khushbu Soni
If I do not do type casting to query.list(); to (List)query.list(); it gives me these errors.
如果我不将类型转换为 query.list(); 到（列表）query.list（）；它给了我这些错误。
java.lang.ClassCastException: java.util.ArrayList cannot be cast to antlr.collections.List
java.lang.ClassCastException: java.util.ArrayList 不能转换为 antlr.collections.List
on calling a method
在调用方法时
category= new Category();
ArrayList data= (ArrayList) category.getCategoryInfo();
and method is
方法是
public List getCategoryInfo(){
Session session = HibernateUtil.openSession();
String sql = "SELECT category.id as id, category.name,c.name as parent_category FROM category join category as c on c.id=category.parent_id";
SQLQuery query = session.createSQLQuery(sql);
query.setResultTransformer(Criteria.ALIAS_TO_ENTITY_MAP);
List data = (List) query.list();
return data;
}
Please help me what is wrong with this code.
请帮我看看这段代码有什么问题。
采纳答案by Sabir Khan
You need to change line, List data = (List) query.list();to List data = query.list();as query.list();always returns a Listso no need to explicit casting.
你需要改变路线， List data = (List) query.list();以 List data = query.list();作为query.list();总是返回List所以无需显式类型转换。
Also , at assignment part, you again need to program on Interface Listbut you are doing on concrete class - ArrayList.
此外，在作业部分，您再次需要编程，Interface List但您正在具体类 - ArrayList.
ArrayList data= (ArrayList) category.getCategoryInfo();needs to be changed to List data= category.getCategoryInfo();
ArrayList data= (ArrayList) category.getCategoryInfo();需要改为 List data= category.getCategoryInfo();
When you program on super type interfaces, need to explicit casting is eliminated.
当您在超类型接口上编程时，不需要显式转换。
Note that Listinterface returned from method getCategoryInfo()and one written at assignment part should be the same interfaces ( either java.util.ListOR antlr.collections.List, you can't mix the two ).
需要注意的是List，从方法返回的接口getCategoryInfo()，一个在分配部分写应该是相同的接口（无论是java.util.List或antlr.collections.List，你不能混用两种）。
Figure out on your own about the kind of Listreturned by query.list();
自己弄清楚List返回的类型query.list();
回答by Diego Farias
It seems like you've imported the wrong List class. Look at the imports of your class and replace antlr.collections.List for java.util.List.
您似乎导入了错误的 List 类。查看您的类的导入并将 antlr.collections.List 替换为 java.util.List。
