split(" +") and split(" ") are different

Question

I want to erase the vacuum in the String.

String input = "java example.java       aaa     bbb";
String[] temp = input.trim().split(" ");

that result is

java
example.java




aaa




bbb

but i want result that

java
example.java
aaa
bbb

so, i use the split(" +"). The result is right. but i don't understand, how doing the split(" +").

Answer 1

split() takes a regex as it's argument. "+" in regex means "one or more of the previous element". So splitting on " +" will split on "one or more spaces".