Split string with dot as delimiter

Question

I am wondering if I am going about splitting a string on a . the right way? My code is:

String[] fn = filename.split(".");
return fn[0];

I only need the first part of the string, that's why I return the first item. I ask because I noticed in the API that . means any character, so now I'm stuck.

Answer 1

Usually its NOT a good idea to unmask it by hand. There is a method in the Pattern class for this task:

java.util.regex
static String quote(String s) 

Answer 2

As DOT( . ) is considered as a special character and split method of String expects a regular expression you need to do like this -

String[] fn = filename.split("\\.");
return fn[0];

In java the special characters need to be escaped with a "\" but since "\" is also a special character in Java, you need to escape it again with another "\" !

Answer 3

split takes a regex as argument. So you should pass "\." instead of "." because "." is a metacharacter in regex.

Answer 4

split() accepts a regular expression, so you need to escape . to not consider it as a regex meta character. Here's an exemple :

String[] fn = filename.split("\\."); 
return fn[0];

Answer 5

String str="1.2.3";
String[] cats = str.split(Pattern.quote("."));

Answer 6

the String#split(String) method uses regular expressions. In regular expressions, the "." character means "any character". You can avoid this behavior by either escaping the "."

filename.split("\\.");

or telling the split method to split at at a character class:

filename.split("[.]");

Character classes are collections of characters. You could write

filename.split("[-.;ld7]");

and filename would be split at every "-", ".", ";", "l", "d" or "7". Inside character classes, the "." is not a special character ("metacharacter").