这个请求头数据的获取逻辑不是很懂，也不明白这里的遍历为什么是用**while**，有大佬能解释一下吗？

package com.cherry.requset;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.Enumeration;

@WebServlet("/RequestHander")
public class RequestHander extends HttpServlet {
   protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

   }

   protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

       //1.获取所有请求头名称
       Enumeration<String> headerNames = request.getHeaderNames();
       //2.遍历
       while (headerNames.hasMoreElements()){
           String name = headerNames.nextElement();
           //3.根据名称获取请求头得值
           String value = request.getHeader(name);
           System.out.println(name+"---"+value);
       }
   }
}