如何用JAVA语句判断邮箱的正确格式？

这周在java课程中学习了怎样 判断邮箱地址的对错。

 //接受 用户输入的一个电子邮件地址，判断格式是否正确。

//判断内容

//1 )、必须包含‘@’和‘，’符号

//2 )、@符号必须在.符号之前

//3 )、@和.符号的前后以及中间必须有内容

下边来看看我的代码吧！

import ;

public class Exercise {

                                    public static void main(String[] args) {

                                                                             ("输入邮箱地址");
                                                                              Scanner scan = new Scanner();
                                                                               String s = ();
                                                                                int a = ("@");
                                                                                int b = (",");
                                                                            if(a == -1 || b == -1 || a > b)
                                                                            ("输入错误");
                                                                             else if(("@", a+1)!=-1)

                                                                             ("输入两个@");  

                                                          else

                                                       {
                                                  ("输入正确");
                                                                   ("用户名是" + (0,a));
                                                                   ("用户名是" + (a+1,()));
                                                        }
                                                 }


                                                          }