In my filter used into EditText, I want to be sure the user can only set .5 or .0 for decimal values.

Valid values examples:

• 34.5
• 34.0
• 34

Invalid values examples:

• 34.2
• 34.8
• 34.6

I tried this one, but it doesn't work properly: [0-9]*[.]?[0|5]

Thank you very much guys!

CodePudding user response：

You're probably looking for [0-9]*(\.([50][0]*)*)*.

[0-9]*: Any character from 0 to 9, zero or more times [so that just a "." (= 0.0) input is valid]

\.: You need to escape the '.' character, since it usually would mean "any character", and you especifically need the dot there.

[50][0]*: First, either five or zero (once). Second, the 0 character, zero or more times (since 35.50 = 35.5). This also avoids inputs like 35.59 from being valid, since 9 != 0.

([50][0]*)*: This occurrence zero or more times, so that 35., for instance, becomes a valid input (since 35. = 35.0).

(\.([50][0]*)*)*: As for this grouping, it's in order to check for the five or the zero only if there is a decimal dot. It's grouping the dot character and the 5/0 logic together with a star (zero or more times) at the end, so if it doesn't occur, it still matches.

Let me know if this was what you were looking for.

CodePudding user response：

To verify the whole numbers in the examples, you can make the last part optional and use anchors.

^[0-9] (?:[.][05])?$

• ^ Start of string
• [0-9] Match 1 digits 0-9
• (?:[.][05])? Optionally match . and a digit 0 or 5
• $ End of string

See a regex demo.

If you want to be able to only type a pattern like that and also accept empty strings or 34. you can repeat the digit 0 or more times, optionally match . and optionally match either 0 or 5.

^[0-9]*[.]?[05]?$

See another regex demo