java grouping regex fail to match string+text

Question

I wrote this test

@Test
public void removeRequestTextFromRouteError() throws Exception {
    String input = "Failed to handle request regression_4828 HISTORIC_TIME from=s:33901510 tn:27825741 bd:false st:Winifred~Dr to=s:-1 d:false f:-1.0 x:-73.92752 y:40.696857 r:-1.0 cd:-1.0 fn:-1 tn:-1 bd:true 1 null false null on subject RoutingRequest";
    final String answer = stringUtils.removeRequestTextFromError(input);
    String expected = "Failed to handle request _ on subject RoutingRequest";
    assertThat(answer, equalTo(expected));
}

which runs this method, but fails

public String removeRequestTextFromError(String answer) {
    answer = answer.replaceAll("regression_\\d\\[.*?\\] on subject", "_ on subject");
    return answer;

}

The input text stays the same and not replaced with "_"

how can I change the pattern matching to fix this?

Did you try printing the result you get from your remove.. method? — TheLostMind
– TheLostMind, Commented Sep 4, 2016 at 7:42
Use return answer.replaceAll("regression_\\d.* on subject", "_ on subject"); inside the removeRequestTextFromError method. — anubhava
– anubhava, Commented Sep 4, 2016 at 7:50

TheLostMind · Accepted Answer · 2016-09-04 07:44:03Z

1

You are using the a wrong regex. You are escaping [ and ] (not necessary at all) and using \\d instead of \\d+. Also, you should use a positive look-ahead instead of actually selecting and replacing the String "on subject"

Use :

public static void main(String[] args) {
    String input = "Failed to handle request regression_4828 HISTORIC_TIME from=s:33901510 tn:27825741 bd:false st:Winifred~Dr to=s:-1 d:false f:-1.0 x:-73.92752 y:40.696857 r:-1.0 cd:-1.0 fn:-1 tn:-1 bd:true 1 null false null on subject RoutingRequest";
    final String answer = input.replaceAll("regression_.* (?=on subject)", "_ ");
    System.out.println(answer);
    String expected = "Failed to handle request _ on subject RoutingRequest";
    System.out.println(answer.equals(expected));
}

O/P :

Failed to handle request _ on subject RoutingRequest
true

answered Sep 4, 2016 at 7:44

TheLostMind

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2 Comments

Elad Benda Over a year ago

i want to add regression_\\d+

TheLostMind Over a year ago

@EladBenda - Yes, you could do that

Tim Biegeleisen · Accepted Answer · 2016-09-04 07:55:19Z

1

As an alternative to the answer given by @TheLostMind, you can try breaking your input into 3 pieces, the second piece being what you want to match and then remove.

Each quantity in parentheses, if matched, will be available as a capture group. Here is the regex with the capture groups labelled:

(.*)(regression_\\d+.* on subject)(.*)
 $1             $2                 $3

You want to retain $1 and $3:

public String removeRequestTextFromError(String answer) {
    answer = answer.replaceAll("(.*)(regression_\\d+.* on subject)(.*)", "$1$3");
}

edited Sep 4, 2016 at 7:55

answered Sep 4, 2016 at 7:45

Tim Biegeleisen

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