How to split a List of Strings in Java with a regex that uses the last occurrence of given Pattern?

Question

I'm pretty new to the regex world. Given a list of Strings as input, I would like to split them by using a regex of punctuations pattern: "[!.?\\n]" .

The thing is, I would like to specify that if there are multiple punctuations together like this:

input: "I want it now!!!"

output: "I want it now!!"

input: "Am I ok? Yeah, I'm fine!!!"

output: [ "Am I ok" , "Yeah, I'm fine!!" ]

Answer 1

You can use

[!.?\n](?![!.?\n])

Here, a ! , . , ? or newline are matched only if not followed with any of these chars.

Or, if the char must be repeated:

([!.?\n])(?!\1)

Here, a ! , . , ? or newline are matched only if not followed with exactly the same char.

See the regex demo #1 and the regex demo #2 .

See a Java demo :

String p = "[!.?\n](?![!.?\n])";
String p2 = "([!.?\n])(?!\\1)";
String s = "I want it now!!!";
System.out.println(Arrays.toString(s.split(p)));  // => [I want it now!!]
System.out.println(Arrays.toString(s.split(p2))); // => [I want it now!!]
s = "Am I ok? Yeah, I'm fine!!!";
System.out.println(Arrays.toString(s.split(p)));  // => [Am I ok,  Yeah, I'm fine!!]
System.out.println(Arrays.toString(s.split(p2))); // => [Am I ok,  Yeah, I'm fine!!]

Answer 2

The split() methos of String accept as delimitator a regular expression.

Ref.: https://docs.oracle.com/javase/7/docs/api/java/lang/String.html#split(java.lang.String)

Example:

String str = "Am I ok? Yeah, I'm fine!!!";
String delimiters = "[!.?\n]";

String[] splitted = str.split(delimiters);
    
for(String part : splitted) {
   System.out.print(part + "\n");
} 

Output:

Am I ok

Yeah, I'm fine