You can use String#toCharArray()
method:
String str = "hello";
char[] arr = str.toCharArray();
As for your question, when you split on an empty string, you will get the first element as empty string, because, your string starts with an empty string, and after every character also, there is an empty string.
So, the first split occurs before the first character.
h e l l o
^ ^ ^ ^ ^ ^
"Split location"
The trailing empty strings are discarded, as specified in documentation:
Trailing empty strings are therefore not included in the resulting array.
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