我的第一个spring代码出错

我遵循了《学习spring应用程序开发》一书下载的pdf中的第一个示例（从22页开始）。我完全按照书中的说明遵循了所有步骤。 我在greetUser（）的下面一行MainClass.java中看到一条红色下划线

System.out.println(greetingMessageService.greetUser());

package org.springframework.chapter1.main;

import org.springframework.chapter1.service.GreetingMessageService;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;


public class MainClass {
    public static void main(String[] args) {          

        ApplicationContext context = new  ClassPathXmlApplicationContext("beans.xml");     

        GreetingMessageService greetingMessageService =  context.getBean("greetingMessageServiceImpl",  GreetingMessageService.class);  

        System.out.println(greetingMessageService.greetUser());   
        } 

}

GreetingMeessageService.java

package org.springframework.chapter1.service;

   public interface GreetingMessageService {

     public String greetUser();

   }

GreetingMessageServiceImpl.java

package org.springframework.chapter1.service;
import org.springframework.stereotype.Service;
@Service 
public class GreetingMessageServiceImpl  implements  GreetingMessageService 
{

 public String greetUser() {         

return "Welcome to Spring";   
}
}

MainClass.java

System.out.println(greetingMessageService.greetUser());

package org.springframework.chapter1.main;

import org.springframework.chapter1.service.GreetingMessageService;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;


public class MainClass {
    public static void main(String[] args) {          

        ApplicationContext context = new  ClassPathXmlApplicationContext("beans.xml");     

        GreetingMessageService greetingMessageService =  context.getBean("greetingMessageServiceImpl",  GreetingMessageService.class);  

        System.out.println(greetingMessageService.greetUser());   
        } 

}

beans.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.1.xsd">


<context:component-scan  base-package="org.springframework.chapter1.service"/>


</beans>

红线神奇地消失了？？我花了2个小时来摆脱它，但它突然消失了。

错误是？？？在System.out.println（greetingMessageService.greetUser（））行中的greetUser（）下有一个红色下划线；在MainClass.java中。为什么？错误是什么。某处有个消息。。。如果你不知道错误信息，红线可能有成千上万的原因，这将很难帮助你。@Deinum它神奇地消失了。谢谢you@Denium我无法接受我自己的答案，请有人帮我把它关闭。