java - Trim a string based on the string length

Question

I want to trim a string if the length exceeds 10 characters.

Suppose if the string length is 12 (String s="abcdafghijkl"), then the new trimmed string will contain "abcdefgh..".

How can I achieve this?

Answer 1

s = s.substring(0, Math.min(s.length(), 10));

Using Math.min like this avoids an exception in the case where the string is already shorter than 10.

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Notes:

1. The above does simple trimming. If you actually want to replace the last characters with three dots if the string is too long, use Apache Commons StringUtils.abbreviate; see @H6's solution. If you want to use the Unicode horizontal ellipsis character, see @Basil's solution.

2. For typical implementations of String, s.substring(0, s.length()) will return s rather than allocating a new String.

3. This may behave incorrectly¹ if your String contains Unicode codepoints outside of the BMP; e.g. Emojis. For a (more complicated) solution that works correctly for all Unicode code-points, see @sibnick's solution.

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^{1 - A Unicode codepoint that is not on plane 0 (the BMP) is represented as a "surrogate pair" (i.e. two char values) in the String. By ignoring this, we might trim the string to fewer than 10 code points, or (worse) truncate it in the middle of a surrogate pair. On the other hand, String.length() is not a good measure of Unicode text length, so trimming based on that property may be the wrong thing to do.}