过滤链的一点问题

package filter;

import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

public class FilterC implements Filter {

  @Override
  public void destroy() {
    // TODO Auto-generated method stub

  }

  @Override
  public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
      throws IOException, ServletException {
    // TODO Auto-generated method stub
    try {
      Thread.sleep(3000);
    } catch (InterruptedException e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
    }
    chain.doFilter(request, response);
    
    try {
      Thread.sleep(3000);
    } catch (InterruptedException e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
    }
    System.out.println("I am " + this.getClass().getSimpleName());

  }

  @Override
  public void init(FilterConfig arg0) throws ServletException {
    // TODO Auto-generated method stub

  }

}

package filter;

import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

public class FilterB implements Filter {

  @Override
  public void destroy() {
    // TODO Auto-generated method stub

  }

  @Override
  public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
      throws IOException, ServletException {
    // TODO Auto-generated method stub
    chain.doFilter(request, response);
    System.out.println("I am " + this.getClass().getSimpleName());

  }

  @Override
  public void init(FilterConfig arg0) throws ServletException {
    // TODO Auto-generated method stub

  }

}

package filter;

import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

public class FilterA implements Filter {

  @Override
  public void destroy() {
    // TODO Auto-generated method stub

  }

  @Override
  public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
      throws IOException, ServletException {
    // TODO Auto-generated method stub
    chain.doFilter(request, response);
    System.out.println("I am " + this.getClass().getSimpleName());

  }

  @Override
  public void init(FilterConfig arg0) throws ServletException {
    // TODO Auto-generated method stub

  }

}

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">
  <display-name>filter-chain</display-name>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list>
    <filter>
        <filter-name>A</filter-name>
        <filter-class>filter.FilterA</filter-class>
    </filter>
     <filter>
        <filter-name>B</filter-name>
        <filter-class>filter.FilterB</filter-class>
    </filter>   
    <filter>
        <filter-name>C</filter-name>
        <filter-class>filter.FilterC</filter-class>
    </filter>   
    
    <filter-mapping>
        <filter-name>A</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>
    <filter-mapping>
        <filter-name>B</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>
    <filter-mapping>
        <filter-name>C</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>  
</web-app>

package filter;

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

/**
 * Servlet implementation class HelloServlet
 */
@WebServlet("/hello")
public class HelloServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public HelloServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		response.getWriter().println("hello world");
		System.out.println("hello world");
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}

}

只有第一个class里面我在chain.dofilter方法前后各加了休眠，其他的都和老师在2-8里面的代码一样，

问下我这段代码访问servlet以后再控制台会打印出 

hello world

I am FilterC

I am FilterB

I am FilterA

不是太能理解，当代码回传到filterC的时候，通过chain.dofilter不是已经像前传递了，同时我在它下面设置了休眠，为什么系统不先打印filterb 和 filtera呢？ 

我以为会是： 

hello world,

I am FilterB

I am FilterA

I am FilterC 

这个顺序的。