Retrieve characters from a string

What is the best way to get a list of characters [a-z] from a string ignoring any other special charac开发者_运维技巧ter or number?

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You could use a regular expression:

String lettersOnly = original.replaceAll("[^a-z]", "");

or

String lettersOnly = original.replaceAll("[^a-zA-Z]", "");

While you can use Unicode groups too, I personally find it easier to recognise and understand a simple set such as a-z or a-zA-Z - it means I don't need to look up whether it will include non-ASCII characters :)

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Limiting yourself to a-z might remove characters you want. e.g. it remove uppercase and letters other than a-z. You might prefer to try

String alphaOnly = text.replaceAll("[^\\p{Alpha}]", "");

This includes upper and lower case letters from any language.