You need to escape the dot if you want to split on a literal dot:
String extensionRemoved = filename.split("\\.")[0];
Otherwise you are splitting on the regex ., which means "any character".
Note the double backslash needed to create a single backslash in the regex.
You're getting an ArrayIndexOutOfBoundsException because your input string is just a dot, ie ".", which is an edge case that produces an empty array when split on dot; split(regex) removes all trailing blanks from the result, but since splitting a dot on a dot leaves only two blanks, after trailing blanks are removed you're left with an empty array.
To avoid getting an ArrayIndexOutOfBoundsException for this edge case, use the overloaded version of split(regex, limit), which has a second parameter that is the size limit for the resulting array. When limit is negative, the behaviour of removing trailing blanks from the resulting array is disabled:
".".split("\\.", -1) // returns an array of two blanks, ie ["", ""]
ie, when filename is just a dot ".", calling filename.split("\\.", -1)[0] will return a blank, but calling filename.split("\\.")[0] will throw an ArrayIndexOutOfBoundsException.
You need to escape the dot if you want to split on a literal dot:
String extensionRemoved = filename.split("\\.")[0];
Otherwise you are splitting on the regex ., which means "any character".
Note the double backslash needed to create a single backslash in the regex.
You're getting an ArrayIndexOutOfBoundsException because your input string is just a dot, ie ".", which is an edge case that produces an empty array when split on dot; split(regex) removes all trailing blanks from the result, but since splitting a dot on a dot leaves only two blanks, after trailing blanks are removed you're left with an empty array.
To avoid getting an ArrayIndexOutOfBoundsException for this edge case, use the overloaded version of split(regex, limit), which has a second parameter that is the size limit for the resulting array. When limit is negative, the behaviour of removing trailing blanks from the resulting array is disabled:
".".split("\\.", -1) // returns an array of two blanks, ie ["", ""]
ie, when filename is just a dot ".", calling filename.split("\\.", -1)[0] will return a blank, but calling filename.split("\\.")[0] will throw an ArrayIndexOutOfBoundsException.
The dot "." is a special character in java regex engine, so you have to use "\\." to escape this character:
final String extensionRemoved = filename.split("\\.")[0];
This handles all delim values:
String str = "21.12.2015";
String delim = "."; // or "-" or "?" or ...
String[] st = str.split(java.util.regex.Pattern.quote(delim));
When you say split you are using delim as a regex pattern. It is treated differently. Please have a look to this regular expression.
But when you are using delim in sysout you are using it as string. the difference is obviuos
split() accepts a regular expression, so you need to escape . to not consider it as a regex meta character. Here's an example :
String[] fn = filename.split("\\.");
return fn[0];
I see only solutions here but no full explanation of the problem so I decided to post this answer
Problem
You need to know few things about text.split(delim). split method:
- accepts as argument regular expression (regex) which describes delimiter on which we want to split,
- if
delimexists at end oftextlike ina,b,c,,(where delimiter is,)splitat first will create array like["a" "b" "c" "" ""]but since in most cases we don't really need these trailing empty strings it also removes them automatically for us. So it creates another array without these trailing empty strings and returns it.
You also need to know that dot . is special character in regex. It represents any character (except line separators but this can be changed with Pattern.DOTALL flag).
So for string like "abc" if we split on "." split method will
- create array like
["" "" "" ""], - but since this array contains only empty strings and they all are trailing they will be removed (like shown in previous second point)
which means we will get as result empty array [] (with no elements, not even empty string), so we can't use fn[0] because there is no index 0.
Solution
To solve this problem you simply need to create regex which will represents dot. To do so we need to escape that .. There are few ways to do it, but simplest is probably by using \ (which in String needs to be written as "\\" because \ is also special there and requires another \ to be escaped).
So solution to your problem may look like
String[] fn = filename.split("\\.");
Bonus
You can also use other ways to escape that dot like
- using character class
split("[.]") - wrapping it in quote
split("\\Q.\\E") - using proper Pattern instance with
Pattern.LITERALflag - or simply use
split(Pattern.quote("."))and let regex do escaping for you.