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javareplaceall
Fruitdrops13
Fruitdrops13

Reputation: 21

Java replaceAll - Replace "/**" with ""

I am currently doing comment analysis with some Java code and needed to do the following opperation:

comment = comment.replaceAll("/**", "");

But I am meet with this Exception:

    Exception in thread "main" java.util.regex.PatternSyntaxException: Dangling meta character '*' near index 2
/**
  ^
    at java.util.regex.Pattern.error(Unknown Source)
    at java.util.regex.Pattern.sequence(Unknown Source)
    at java.util.regex.Pattern.expr(Unknown Source)
    at java.util.regex.Pattern.compile(Unknown Source)
    at java.util.regex.Pattern.<init>(Unknown Source)
    at java.util.regex.Pattern.compile(Unknown Source)
    at java.lang.String.replaceAll(Unknown Source)
    at commentCoupler.coupler.commentCriteriaForfilled(coupler.java:234)
    at commentCoupler.coupler.analyze(coupler.java:64)
    at commentCoupler.coupler.recursiveCoupler(coupler.java:27)
    at commentCoupler.coupler.recursiveCoupler(coupler.java:22)
    at commentCoupler.coupler.recursiveCoupler(coupler.java:22)
    at commentCoupler.main.main(main.java:16)

Edit: The exception also occurs when I do

comment = comment.replaceAll("**/", "");

and

comment = comment.replaceAll("*/", "");

Do anyone know why this happens and do anyone have a workaround?

Upvotes: 0

Views: 4098

Answers (4)

Captain Man
Captain Man

Reputation: 7705

Two things are wrong with this code:

comment = comment.replaceAll("/**", "");
  1. * is a special regex character to match any number of any characters, based on the context that you are removing comments you want to match the literal * so you need your regex to be /\*\*.
  2. Because this regex is inside a java String it will try to read \* as an escape code (like \n being newline character), but \* isn't one. It needs to be \\* instead, meaning the String should be /\\*\\*

This is correct.

comment = comment.replaceAll("/\\*\\*", "");

As an aside, even if \* was a valid escape code, the thing it got replaced with would be passed into regex, not \*. (e.g., if you put \n in the newline character would go into regex, not a backslash and a lowercase n.

You may want to go with something like this though

comment = comment.replaceAll("/\\**\\*/", "");

which would be removing /* <stuff> */. This catches doc-comments and regular multi-line comments in addition to removing the entire comment. It depends on how you've read the string though.

Upvotes: 0

srcarro
srcarro

Reputation: 61

First parameter of "replaceAll" is a regular expression, and character "*" has a special meaning in regular expressions.

You can use something like this:

String a = "/**hola mundo/**, adios mundo";
String output = a.replaceAll("/\\*\\*", "");
System.out.println(output); // --> "hola mundo, adios mundo"

Upvotes: 2

Dagriel
Dagriel

Reputation: 574

comment = comment.replaceAll("/\**", "");

Upvotes: 0

aioobe
aioobe

Reputation: 421040

replaceAll takes a regular expression, and /** isn't a valid regular expression.

If you just want to remove /**, use replace instead.

Upvotes: 6

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