Question

i want to check if the string i take from a Textfield
has a comma, in order to drop it and ask for a new value with dot.

i try to use

  textTestAr.trim().matches("^[,]+$")     

but nothing happens, while this

        ^[1-9,]+$      

does the trick, but also matches numbers like 1.

Answer 1

The caret ^ matches the beginning of the text. [,]+ matches an arbitrary number of commas. What you need is something to ignore everything before and after the item you are looking for:

^.*[,].*$

The dot matches any character except newline. * is repetition (0 — any number). The $ matches the end of text.

Note that trimming the string is unnecessary here.