Java Regular Expression <elipses>

Question

I am reading though some old code that seems to aim to take out a sequence of periods (......) in a table of contents. It utilizes a java regular expression to accomplish this. This is the code that was used.

input = input.replaceAll( ".*<elipses>.*", "" );

However I don't see mention of a regex with "<>'s" except here:

Special constructs (named-capturing and non-capturing)
(?<name>X) X, as a named-capturing group

(http://docs.oracle.com/javase/7/docs/api/java/util/regex/Pattern.html)

What does the <elipsis> mean?

Are you sure you don't have literally <elipses> in your text? .* is greedy so I don't see how <elipses> would work as a match for .... — Sotirios Delimanolis
– Sotirios Delimanolis, Commented Mar 21, 2014 at 16:58
Is that actually the literal code copied and pasted, as opposed to something out of documentation? — chrylis -cautiouslyoptimistic-
– chrylis -cautiouslyoptimistic-, Commented Mar 21, 2014 at 16:58
The above code is what was in the old code. I was just trying to understand what they were originally trying to do. It is not out of Java's documentation. — 9er
– 9er, Commented Mar 21, 2014 at 16:59

Mena · Accepted Answer · 2014-03-21 17:09:13Z

3

That looks like a Java 7 named group with what appears to be incorrect syntax.

The correct syntax would be something like:

//                           | named group "stuff" matches 0 or more characters
//                           |           | named group "ellipses" 3 consecutive dots
//                           |           |                     | non grouped stuff
Pattern p = Pattern.compile("(?<stuff>.*)(?<ellipses>\\.\\.\\.).*");
String input = "blah ... blah";
Matcher m = p.matcher(input);
if (m.find()) {
    // printing back reference to named group "stuff"
    System.out.println(m.group("stuff"));
    // printing back reference to named group "ellipses"
    System.out.println(m.group("ellipses"));
}

Output

blah 
...

Otherwise your Pattern is attempting to actually match some markup containing <ellipses>, preceded by any number of characters, followed by the same.

Some API reference to Java 7 named groups here.

edited Mar 21, 2014 at 17:09

answered Mar 21, 2014 at 17:02

Mena

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1 Comment

Sotirios Delimanolis Over a year ago

Cool that you can do this.

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