Question

我想在这些条件下检查字符串是true还是false：

1. the string must be 5 charecters long
2. 3rd charecter should be 'b'
3. the string must contain special charecter like '?' or '@' and '$'

我无法确定我还做了什么：

System.out.println("//b//b//b?//b//b//b" ,"akb?g");//this is totally wrong though

Answer 1

尝试使用此模式：

^(?=.*[?@$]).{2}b.{2}$

以下是一段代码片段，展示了如何使用此模式：

if ("invalid".matches("(?=.*[?@$]).{2}b.{2}")) {
    System.out.println("invalid matches");
}
if ("12b?3".matches("(?=.*[?@$]).{2}b.{2}")) {
    System.out.println("12b?3 matches");
}

Demo

以下是该模式的简要说明：

^            from the start of the string
(?=.*[?@$])  assert that we see a special character anywhere, at least once
.{2}         then match any two characters
b            match a 'b' for the 3rd character
.{2}         then match any two characters again
$            end of string

Answer 2

如果你的意思是＆＃39;？＆＃39;或（＆＃39; @＆＃39;和＆＃39; $＆＃39;）使用此

(
   (?=.*[\$?])      // Must contain either $ or ?
   (?=.*[@?])       // Must contain either @ or ?
    ..b..$          // Third character should be b
)

一行

((?=.*[\$?])(?=.*[@?])..b..$)

检查String是否包含某些字符Java Regular Expression

2 个答案:

Demo