CODEWITHSUNDEEP
javaregexregex-groupregex-negation
Simeon Leyzerzon
Simeon Leyzerzon

Reputation: 19084

How to filter out a string with regular expression

Let's say I want a regex expressing a filter selecting a string of a particular shape only if it doesn't end in a specific suffix, for example:

whereas

Sounds like a composite of something like [\d\w] with !.writing, but unsure how to express such a combo in a valid regex expression.

What can I try next?

Upvotes: 1

Views: 164

Answers (3)

DigitShifter
DigitShifter

Reputation: 854

Alternative regex:

"^(?:\w+\.)+\w+$" and "\.writing$"

Regex in testbench and context:

public static void main(String[] args) {
    List<String> inputs = List.of("AaA.BbB.CcC.DdD.EeE", "a1.b2.c3.d4.e5", "AaA.BbB.CcC.DdD.EeE.writing", "a1.b2.c3.d4.e5.writing");

    for (String input: inputs) {
        printResult(input);
    }
}

private static void printResult(String input) {
    // Pattern allowedPattern = Pattern.compile("^(?:\\w+\\.)+\\w+$"); -> \\w will match 'A word character: [a-zA-Z_0-9]'
    // Pattern allowedPattern = Pattern.compile("^(?:[a-zA-Z0-9]+\\.){4}[a-zA-Z0-9]+$"); -> if you know that it always going to be 4 sections with ending dot, and the last section with no dot

    Pattern allowedPattern = Pattern.compile("^(?:[a-zA-Z0-9]+\\.)+[a-zA-Z0-9]+$");
    Pattern notAllowedSuffixPattern = Pattern.compile("\\.writing$");
    System.out.println("Incoming input: " + input);
    String result = (!notAllowedSuffixPattern.matcher(input).find() && allowedPattern.matcher(input).find())
            ? "Matching.\n"
            : "Not Matching!\n";
    System.out.println(result);
}

Output:

Incoming input: AaA.BbB.CcC.DdD.EeE
Matching.

Incoming input: a1.b2.c3.d4.e5
Matching.

Incoming input: AaA.BbB.CcC.DdD.EeE.writing
Not Matching!

Incoming input: a1.b2.c3.d4.e5.writing
Not Matching!

Upvotes: 1

ABaumstumpf
ABaumstumpf

Reputation: 293

your examples do not really match up.

[\d\w] ìs redundant: \d is [0-9] but \w already is matching that with [a-zA-Z_0-9],

And you say

AaA.BbB.CcC.DdD.EeE.writing or a1.b2.c3.d4.e5.writing shouldn't due to the .writing suffix.

Now if you only care about if it matches or not then you can check if there is a match for the prohibited ending and negate your following logic.

String inputString = <your-input>;
if( Pattern.compile("\\w*\\.writing$").matcher(inputstring).matches() ) {
 // no match - so the string is "valid"
}

Upvotes: 1

Gilles Qu&#233;not
Gilles Qu&#233;not

Reputation: 185790

With grep:

AaA.BbB.CcC.DdD.EeE
a1.b2.c3.d4.e5
AaA.BbB.CcC.DdD.EeE.writing

$ grep -v '.writing' file
AaA.BbB.CcC.DdD.EeE
a1.b2.c3.d4.e5

Upvotes: 0

Related Questions