Question

I want a java regex expression that accepts only the numbers and dots.

for example,

             1.1.1 ----valid
             1.1   ----valid
             1.1.1.1---valid
             1.    ----not valid

The dots should not be at the starting position or at the ending position.

Answer 1

I guess this is what you want:

^\d+(\.\d+)*$

Explanation: It accepts numbers separated by dots; it starts and ends with number; a number can have multiple digits; one number without dots is also accepted.

Variant without multiple digits:

^\d(\.\d)*$

Variants where at least one dot is required:

^\d+(\.\d+)+$
^\d(\.\d)+$

Don’t forget that in Java you have to escape the \ symbols, so the code will look like this:

Pattern NUMBERS_WITH_DOTS = Pattern.compile("^\\d+(\\.\\d+)*$");