CODEWITHSUNDEEP
javaregex
masterfly
masterfly

Reputation: 951

Regular Expression for specific number of special character

I need only specific number of special characters in a password. I tried the following regex

(?=.*[$@!%*?&]{1})

It takes special character from that set but accepts even multiple special characters.

{1} means number of characters from the set I am allowing the string to validate.

For example,

Alpha1? should be true for the above regular expression

@lpha1? should not be validated by above regex because now it has 2 characters from that set.

Can someone please help? Any help is appreciated. Thanks in advance

Upvotes: 0

Views: 1244

Answers (2)

Gurmanjot Singh
Gurmanjot Singh

Reputation: 10360

Try this Regex:

^[^$@!%*?&\n]*[$@!%*?&][^$@!%*?&\n]*$

Explanation:

  • ^ - asserts the start of the string
  • [^$@!%*?&\n]* - matches 0+ occurrences of any character that does NOT fall in these set of characters: $, @, !, %, ?, & or a newline character
  • [$@!%*?&] - matches one occurrence of one of these characters: $, @, !, %, ?, &
  • [^$@!%*?&\n]* - matches 0+ occurrences of any character that does NOT fall in these set of characters: $, @, !, %, ?, & or a newline character
  • $ - asserts the end of the string

Click for Demo

JAVA Code:(Generated here)

import java.util.regex.Matcher;
import java.util.regex.Pattern;

final String regex = "^[^$@!%*?&\\n]*[$@!%*?&][^$@!%*?&\\n]*$";
final String string = "abc12312\n"
     + "$123\n"
     + "$123?\n"
     + "Alpha1?\n"
     + "@lpha1?";

final Pattern pattern = Pattern.compile(regex, Pattern.MULTILINE);
final Matcher matcher = pattern.matcher(string);

while (matcher.find()) {
    System.out.println("Full match: " + matcher.group(0));
    for (int i = 1; i <= matcher.groupCount(); i++) {
        System.out.println("Group " + i + ": " + matcher.group(i));
    }
}

Update:

To get the strings with exactly 2 special characters, use this:

^(?:[^$@!%*?&\n]*[$@!%*?&]){2}[^$@!%*?&\n]*$

To get strings with exactly 5 spl. characters, replace {2} with {5}.

To get string with 2-5 special characters, use {2-5}

Upvotes: 2

f1l2
f1l2

Reputation: 491

In Java you can use the method replaceAll to filter all characters up to your set of special characters. The method takes as argument a regular expression. The size of the result represents the count of special characters:

String password = "@foo!";

int size = password.replaceAll("[^$@$!%*?&]","").length();

System.out.println(size);
// will print 2

Upvotes: 1

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