regex to find numbers with unique digits

Question

I want to find 10 digit numbers with no repeat digits, for example:

1123456789 //fail, there are two 1\'s
6758951230 //fail, there are two 5\'s
6789012345 //         


        

Answer 1

This regex works:

^(?!.*(.).*\1)\d{10}$

This uses an anchored negative look ahead with a back reference to assert that there are no repeating characters.

See a live demo working with your examples.

In java:

if (str.matches("^(?!.*(.).*\\1)\\d{10}"))
    // number passes