这有什么问题？我找不到符号

Question

这是类的代码方法的前四行:

这是在类"CrudController"

public String create(Object entity, Class clazz, String req_id, HttpServletResponse response) throws NullPointerException {
    if (entity == null ) throw NullPointerException("ENTITY");
    else if(clazz == null) throw NullPointerException("CLAZZ");
            else if(response == null) throw NullPointerException("RESPONSE");

我在这三行中遇到这些错误:

[ERROR] /path/to/CrudController.java:[42,29] error: cannot find symbol
[ERROR]  class CrudController
[ERROR] /path/to/CrudController.java:[43,31] error: cannot find symbol
[ERROR]  class CrudController
[ERROR]/pathto/CrudController.java:[44,48] error: cannot find symbol
[ERROR]  class CrudController

位置编号(29,31和48在'=='的开头是正确的

Answer 1

更改所有throw NullPointerException(STRING);以throw new NullPointerException(STRING);

在这里你抛出异常.异常是相应的Exception类型类的实例,因此您需要抛出一个new需要关键字的实例.

public String create(Object entity, Class clazz, String req_id, HttpServletResponse     response) throws NullPointerException {
if (entity == null ) throw new NullPointerException("ENTITY");
else if(clazz == null) throw new NullPointerException("CLAZZ");
        else if(response == null) throw new NullPointerException("RESPONSE");