java - 在 '@'之前屏蔽电子邮件中的中间字符

Question

我只想显示电子邮件的前两个字符和后两个字符，如下所示:

Email -  123456789@gmail.com
result - 12*****89@gmail.com

我正在使用此正则表达式将匹配项替换为*-(?<=.{2}).*(?=.{2}@)。
使用的代码段:

String email = "123456789@gamil.com";
System.out.println(email.replaceAll("(?<=.{3}).*(?=.{3}@)", "*"));

// prints - 12**89@gamil.com
// Adds only 2 ** in the middle
// Required * for each replaced character like - 12*****89@gmail.com

即使正则表达式匹配正确的东西，它总是用**替换中间部分。但是我想要每个字符一个*。有什么问题以及如何解决？

Answer 1

在Kotlin中使用

val s = "123456789@gmail.com"
val p = """^([^@]{2})([^@]+)([^@]{2}@)""".toRegex()
println(s.replace(p) { 
    it.groupValues[1] + "*".repeat(it.groupValues[2].length) + it.groupValues[3]
})

参见proof。
结果:12*****89@gmail.com。
模式说明

--------------------------------------------------------------------------------
  ^                        the beginning of the string
--------------------------------------------------------------------------------
  (                        group and capture to \1:
--------------------------------------------------------------------------------
    [^@]{2}                  any character except: '@' (2 times)
--------------------------------------------------------------------------------
  )                        end of \1
--------------------------------------------------------------------------------
  (                        group and capture to \2:
--------------------------------------------------------------------------------
    [^@]+                    any character except: '@' (1 or more
                             times (matching the most amount
                             possible))
--------------------------------------------------------------------------------
  )                        end of \2
--------------------------------------------------------------------------------
  (                        group and capture to \3:
--------------------------------------------------------------------------------
    [^@]{2}                  any character except: '@' (2 times)
--------------------------------------------------------------------------------
    @                        '@'
--------------------------------------------------------------------------------
  )                        end of \3