使用正则表达式按域分组电子邮件登录数据[Java]

Question

我有一个电子邮件列表，看起来如下所示：

james; [e-mail]
george; [e-mail]
alex; [e-mail]
anthony; [e-mail]
mike; [e-mail]

我需要这样组织它们：

james,george - gmail.com
alex,anthony - yahoo.com
mike - outlook.com

我如何在Java使用regex而不使用任何容器类和流来实现这一点呢？

Answer 1

您将必须有映射到存储列表的名称为每个域。您可以对string使用split方法，如下所示：

public static void main(String[] args) throws Exception {
    String [] emails = {
            "james; [e-mail]",
            "george; [e-mail]",
            "alex; [e-mail]",
            "anthony; [e-mail]",
            "mike; [e-mail]"};
    
    Map<String,List<String>> domains = new HashMap<>();
    List<String> names = null;
    
    for(String entry : emails) {
        String[] data = entry.split(";|@");
        if(domains.containsKey(data[2])){
            names = domains.get(data[2]);
        } else {
            names = new ArrayList<>();
            domains.put(data[2], names);
        }
        names.add(data[0]);
    }
    
    for(String key : domains.keySet()) {
        System.out.println(domains.get(key) + " - " + key);
    }
}

输出：

[mike] - outlook.com
[james, george] - gmail.com
[alex, anthony] - yahoo.com

Answer 2

我不知道这和你的意图有多接近，但我试了一下：

String [] emails = {
        "james; [e-mail]",
        "george; [e-mail]",
        "alex; [e-mail]",
        "anthony; [e-mail]",
        "mike; [e-mail]"};

Map<String, String> mailMap = new HashMap<>();

Pattern p = Pattern.compile(" ([a-zA-Z]+)@([a-zA-Z.]+)");

for (String string : emails) {
    Matcher m = p.matcher(string);
    if (m.find( )) {
        String name = m.group(1);
        String mailProvider = m.group(2);
        
        if (mailMap.containsKey(mailProvider)) {
            String oldValue = mailMap.get(mailProvider);
            mailMap.put(mailProvider, oldValue + "," + name);
        } else {
            mailMap.put(mailProvider, name);
        }
        
     } else {
        System.out.println("String did match expected format");
     }
}

for (String mailProvider : mailMap.keySet()) {
    System.out.println(mailMap.get(mailProvider) + " - " + mailProvider);
}