Regex To Split String Into Sentences

Question

I need to split a string containing sentences such as:

"this is a sentence. this is another. Rawlings, G. stated foo and bar." 

into

["this is a sentence.", "this is another.", "Rawlings, G. stated foo and bar."] 

using regular expressions.

The other solutions I found split the third sentence into "Rawlings, G." and "stated foo and bar." which is not what I want.

Answer 1

Regular expressions generally do not solve this problem.

You need a sentence detection algorithm, OpenNLP has one

It's simple enough to use:

String sentences[] = sentenceDetector.sentDetect(yourString);

And handles a lot of tricky cases

• "Walter White Jr. has money"
• "Mr. Pink does not give tips"

Answer 2

Through nested lookbehinds.

Just split your input string according to the below regex. The below regex would split the input string according to the boundary which exists just after to a dot and also it check for the preceding character of dot. It splits only if the preceding character of dot is not an upppercase letter.

String s = "this is a sentence. this is another. Rawlings, G. stated foo and bar.";
String[] tok = s.split("(?<=(?<![A-Z])\\.)");
System.out.println(Arrays.toString(tok));

Output:

[this is a sentence.,  this is another.,  Rawlings, G. stated foo and bar.]

Explanation:

• (?<=(?<![A-Z])\\.) Matches the boundary which exists just after to dot but the dot wouldn't be preceded by an uppercase letter.