The version string that splits into nothing
A easy Java puzzle in the string handling family. One line below contains a real bug. Try to spot it first, then read why it fails and how to fix it.
Highlighted: line 4. Play this one as a puzzle without the answer.
What is wrong
split takes a regular expression, and . matches any character. Every character is a separator, so all the pieces are empty and are removed: the array has length 0 and parts[0] throws.
The fix
How to avoid it next time
Escape regex metacharacters with a double backslash, or use Pattern.quote for literal text.
Want the background? Read Regular expressions in the Java concepts library.
About string handling
Strings are immutable, split and replaceAll take regular expressions, and character encodings default to whatever the platform says. Small misunderstandings produce wrong output rather than errors.
In code review: Look at whether the return value of a String method is used, whether a pattern argument is a regex, and whether an encoding is named explicitly.
More puzzles in this family
Frequently asked questions
What is the bug in "The version string that splits into nothing"?
split takes a regular expression, and . matches any character. Every character is a separator, so all the pieces are empty and are removed: the array has length 0 and parts[0] throws. The faulty line is line 4: String[] parts = version.split(".");
How do I fix it?
Replace it with: String[] parts = "1.18.2".split("\\.");. Escape regex metacharacters with a double backslash, or use Pattern.quote for literal text.
How do I catch string handling in code review?
Look at whether the return value of a String method is used, whether a pattern argument is a regex, and whether an encoding is named explicitly.
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