java - 从段落中提取给定的子字符串

Question

我想执行以下功能:

从给定的段落中提取给定的字符串，例如

String str= "Hello this is paragraph , Ali@yahoo.com . i am entering  random  email here as this one  AHmar@gmail.com " ; 

我要做的是解析整个段落，读取电子邮件地址，并打印他们的服务器名称，我已经尝试使用 for 循环和 substring 方法, 确实使用了 indexOf ，但可能是我的逻辑不太好理解，有人可以帮我吗？

Answer 1

对于这种情况，您需要使用正则表达式。

试试下面的正则表达式:-

String str= "Hello this is paragraph , Ali@yahoo.com . i am " +
            "entering  random  email here as this one  AHmar@gmail.com " ;

Pattern pattern = Pattern.compile("@(\\S+)\\.\\w+");
Matcher matcher = pattern.matcher(str);
while (matcher.find()) {
     System.out.println(matcher.group(1));
}

输出:-

yahoo
gmail

更新:-

这是带有 substring 和 indexOf 的代码:-

   String str= "Hello this is paragraph , Ali@yahoo.com . i am " +
        "entering  random  email here as this one  AHmar@gmail.com " ;

   while (str.contains("@") && str.contains(".")) {

        int index1 = str.lastIndexOf("@");  // Get last index of `@`
        int index2 = str.indexOf(".", index1); // Get index of first `.` after @

        // Substring from index of @ to index of .      
        String serverName = str.substring(index1 + 1, index2);
        System.out.println(serverName);

        // Replace string by removing till the last @, 
        // so as not to consider it next time
        str = str.substring(0, index1);

    }