How to match “any character” in regular expression?

Question

The following should be matched:

AAA123
ABCDEFGH123
XXXX123

can I do: \".*123\" ?

Answer 1

.* and .+ are for any chars except for new lines.

Double Escaping

Just in case, you would wanted to include new lines, the following expressions might also work for those languages that double escaping is required such as Java or C++:

[\\s\\S]*
[\\d\\D]*
[\\w\\W]*

for zero or more times, or

[\\s\\S]+
[\\d\\D]+
[\\w\\W]+

for one or more times.

Single Escaping:

Double escaping is not required for some languages such as, C#, PHP, Ruby, PERL, Python, JavaScript:

[\s\S]*
[\d\D]*
[\w\W]*
[\s\S]+
[\d\D]+
[\w\W]+

Test

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


public class RegularExpression{

    public static void main(String[] args){

        final String regex_1 = "[\\s\\S]*";
        final String regex_2 = "[\\d\\D]*";
        final String regex_3 = "[\\w\\W]*";
        final String string = "AAA123\n\t"
             + "ABCDEFGH123\n\t"
             + "XXXX123\n\t";

        final Pattern pattern_1 = Pattern.compile(regex_1);
        final Pattern pattern_2 = Pattern.compile(regex_2);
        final Pattern pattern_3 = Pattern.compile(regex_3);

        final Matcher matcher_1 = pattern_1.matcher(string);
        final Matcher matcher_2 = pattern_2.matcher(string);
        final Matcher matcher_3 = pattern_3.matcher(string);

        if (matcher_1.find()) {
            System.out.println("Full Match for Expression 1: " + matcher_1.group(0));
        }

        if (matcher_2.find()) {
            System.out.println("Full Match for Expression 2: " + matcher_2.group(0));
        }
        if (matcher_3.find()) {
            System.out.println("Full Match for Expression 3: " + matcher_3.group(0));
        }
    }
}

Output

Full Match for Expression 1: AAA123
    ABCDEFGH123
    XXXX123

Full Match for Expression 2: AAA123
    ABCDEFGH123
    XXXX123

Full Match for Expression 3: AAA123
    ABCDEFGH123
    XXXX123

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If you wish to explore the expression, it's been explained on the top right panel of regex101.com. If you'd like, you can also watch in this link, how it would match against some sample inputs.

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RegEx Circuit

jex.im visualizes regular expressions: