错误消息"非法开始表达"？

Question

// Simple program to understand pass by reference 
import java.util.*;
public class HelloDate {
    public static void main(String args[])
    {
         class Number                     // Contains only an integer
         {
             int i;
         }
         static void f(Number k)           // <<--- Illegal start of expression ???
         {
             k.i = 22;
         } 
         Number n1 = new Number();        // New object of Number
         n1.i = 9;
         f(n1);                           //Passing an object
         System.out.println(n1.i);        // Print
      }
    }  

代码显示错误static void f(Number k).我应该把这个方法void f()放在课堂上吗？如果是,为什么这是必要的？

Answer 1

方法必须是类的成员,它们只能放在类的主体中.