请老司机帮看看如何实现sop方法，下面的代码错误在哪里呢？

import java.util.List;
import java.util.ArrayList;
import java.util.Iterator;



public class Jihejianliduixiang {

    public static void main(String[] args) {
        List list=new ArrayList();
        list.add("WorldHello!");
        list.add("Helloworld!");
        
        Iterator first=list.iterator();
        while(first.hasNext()) {
            System.out.print(first.next()+" ");
        }
        
        sop("集合长度为："+list.size());
        
      public static void sop(Object obj) {
          System.out.println(obj);
      }
    }

}

感谢！