Question

I want to split string by setting all non-alphabet as separator.

String[] word_list = line.split("[^a-zA-Z]");

But with the following input

11:11 Hello World

word_list contains many empty string before “hello” and “world”

Please kindly tell me why. Thank You.

Answer 1

Because your regular expression matches each individual non-alpha character. It would be like separating

",,,,,,Hello,World"

on commas.

You will want an expression that matches an entire sequence of non-alpha characters at once such as:

line.split("[^a-zA-Z][^a-zA-Z]*")

I still think you will get one leading empty string with your example since it would be like separating ",Hello,World" if comma were your separator.