Question

public static void main(String[] args){
    String testStr = "Test test. Test 2. Test3?";
    String[] newStr = testStr.split(".?");
    System.out.print(newStr[0]);
}

I get an Array Index Out of Bounds exception running this, and the length of newStr is 0. I want to break the sentence up into tokens on “.” and “?”. What error am I making?

Answer 1

String#split takes a regular expression as a parameter to split. . and ? have special meaning in regular expressions.

You can use character class to split on either of them:

testStr.split("[.?]");

Inside a character class you don’t need to escape them, as special characters lose meaning inside character class.

If you use it with normal pipe |, you need to escape it: –

testStr.split("\\.|\\?");

UPDATE: – If you want to preserve your delimiters:

testStr.split("(?<=[.?])")