Splitting String by multiple symbols,regex

Question

Regex split through multiple symbols String s="He is a very very good boy, isn't he?"

String[] sa = s.split("[!, ?._'@]");
System.out.println(sa.length);
for (String string : sa) {
    System.out.println(string);
}

11
He
is
a
very
very
good
boy

isn
t
he

while using

String[] sa = s.split("[!, ?._'@]+");

10
He
is
a
very
very
good
boy
isn
t
he

+ in regex ie used for one or more but how this space is coming?

Answer 1

This happens because the split function is creating an array element containing an empty string between the comma , and the spaceafter boy .

arr = ['He', 'is', 'a', 'very', 'very', 'good', 'boy', '', 'isn', 't', 'he']

The function beleives there is some text between the comma and the space when it splits the text, effectively generating that empty string.

When you use the + symbol, you split by "groups" of characters, and it takes the comma and space as the splitting regular expression, not generating that empty string between those characters.