regex - Find pattern in file with java-8

Question

I have found the following solution from a similar question. Here is the link:

   Pattern p = Pattern.compile("is '(.+)'");
    stream1.map(p::matcher)
         .filter(Matcher::matches)
         .findFirst()
         .ifPresent(matcher -> System.out.println(matcher.group(1)));

This is the solution given by khelwood. This is very useful to me. But I don't know why it is not printing anything.

I am trying to match anything that follows the word 'is '.

And my input file contains these lines:

my name is tom
my dog is hom.

I need to print

tom
hom.

But nothing is printed

holi-java · Accepted Answer · 2017-06-25 23:37:48Z

3

you can't get all of the result since Stream#findFirst is return the first satisfied element in a stream, please using Stream#forEach instead.

you should remove the symbol ' that doesn't appear there at all, and replace Matcher#matches with Matcher#find, because Matcher#matches will matches the whole input. for example:

Pattern p = Pattern.compile("is (.+)");
stream1.map(p::matcher)
       .filter(Matcher::find)
       .forEach(matcher -> System.out.println(matcher.group(1)));

edited Jun 25, 2017 at 23:37

answered Jun 25, 2017 at 23:22

holi-java

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Piyush · Accepted Answer · 2017-06-26 00:14:59Z

1

Just remove the single quotes in the regex. I am assuming since you said you want to match anything after 'is', you may want to print a blank if nothing follows 'is'; thus, the '.*' instead of '.+' in the regex I used.

This should work.

 Pattern p = Pattern.compile("is (.*)");
    stream1.map(p::matcher)
         .filter(Matcher::matches)
         .filter(Matcher::find)
         .forEach(matcher -> System.out.println(matcher.group(1)));

edited Jun 26, 2017 at 0:14

answered Jun 25, 2017 at 23:22

Piyush

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1 Comment

Ilak Over a year ago

Thanks, but I am not getting anything still

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