Java regex: match multiple word boundaries

Question

I would like to match couple of words in a text. Have following:

if ( Pattern.matches(".*\\b" + placeSub.toLowerCase() + "\\b" + placeSup.toLowerCase() + "\\b.*", sourceText.toLowerCase()) ) {
    System.out.println( String.format("Matched %s on %s", placeSub, placeSup) );        
}

The variables placeSub, placeSup & sourceText are dynamic (runtime).

The code above doesn't work (no match). However, the following matches:

if ( Pattern.matches(".*\\b" + placeSub.toLowerCase() + "\\s" + placeSup.toLowerCase() + "\\b.*", sourceText.toLowerCase()) ) {
   System.out.println( String.format("Matched %s on %s", placeSub, placeSup) ); 
}

Why is the text able to match \\s and not \\b?

Example input:

placeSub : South
placeSup : Sudan
sourceText : tens of thousands of people have fled fierce fighting in south sudan's northern unity state

With placeSub = South and placeSup = Sudan there can't be just a \b between the two. In the example there is, however, a space, which is why \s matches. — Biffen
– Biffen, Commented May 12, 2015 at 16:04
How I am supposed to match 2 words separated by by unknown characters? The case of South Sudan is just an example. It would be South-Sudan or something else. — Mugoma J. Okomba
– Mugoma J. Okomba, Commented May 12, 2015 at 16:08
@MugomaJ.Okomba If they have to be separate words: /word\b.*\bword/ — Biffen
– Biffen, Commented May 12, 2015 at 16:10
.* matches anything before and anything after. I could have used ^ & $ but preferred to leave the expression open. — Mugoma J. Okomba
– Mugoma J. Okomba, Commented May 12, 2015 at 16:11

anubhava · Accepted Answer · 2015-05-12 16:14:11Z

2

You should actually use:

Pattern.matches(
   ".*?\\b" + placeSub.toLowerCase() + "\\b\\W+\\b" + placeSup.toLowerCase() + "\\b.*",
   sourceText.toLowerCase())

Which will translate into:

/.*?\bsouth\b\W+\bsudan\b.*/i

See regex demo here

answered May 12, 2015 at 16:14

anubhava

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