 Okay, so validating credit card number using regular expression is one of the common usage. On an actual credit card, the digits are usually pledged into group of 4 which makes the credit card easier for humans to read. Almost all of the credit card companies using this number format. So as you can see that this credit card number consisting of 16 digits and these digits are divided into 4 group and each group consisting of 4 digit. So without thinking much, let us write the rejects to match this format. Alright, so here I have added some sample credit card number followed by either hyphen or space. So in the first set, I want to match a digit exactly 4 times. So let us write the rejects. But first let us define the meta character credit sign to asset the beginning of the string and then backslash d4 followed by hyphen or space. So let us use the character class to define hyphen and space. And now I want to repeat this expression to match next to set. So for that, let us group this expression into parenthesis and then let us use repeating quantifier like this. Now lastly we want to repeat the numeric pattern one last time but now without the hyphen or space. So let us use backslash d and asset the end of the string. Now here as you can see that this last credit card number is not matching because that's an invalid credit card number. So this is how we have a working rejects to match credit card numbers, simple right? Now let us move to the next demo. Alright so in this demo we will create a rejects to match simple date format which is of dd slash mm slash yyy. We might think that date validation should be an easy job for the regular expression right? No, it is not. The main issue is that regular expression is not directly dealt with the numbers. I mean we cannot tell a regular expression in a straight forward way to match, hey, match a number between 1 to 31 say for date. So let's jump into the demo to understand what I mean to say. Okay, so here in the input text I have added some random numbers from 1 to 31. Now as I said rejects is not directly dealt with the numbers. So first of all let us write the rejects to match the numbers between 1 to 31. In our case let us assume this is our date. So if I write expression, so as you can see that this expression matches number 30 and 31. Now let us use alternation character and write rejects to match other numbers between 10 to 29. So for that let me add this number in character class followed by 0 to 9. So now this pattern matches the numbers from 10 to 29. Now let us continue with our expression to match this further number which is from 1 to 9. So for that let me add alternation character then 0, 1, 2, 9. So yes now it matches the remaining number from 1 to 9. But you have noticed that this number is still not matching. Why? Because I have not added 0 over here. So if I add 0 then it started matching. But in the date there can be 0 or there can be a not. So let us make the 0 optional by adding question mark over here. So yes now it started matching the all the remaining numbers. So same way we can write the rejects to match the month between 1 to 12. So now let us write the full rejects to match the date. But before that let me add some valid and invalid date in the input text over here. First let us add the carrot sign over here. Okay and this portion is now completed to match the date. So let us add in one group followed by forward slash and then for month if I write like this 0 to 2. Now this portion matches the month number 10, 11 and 12. So for remaining month number let us use alternation character and then 0. And let us make this 0 optional and the last set consisting of 4 digit. So for that let us use backslash D and let us end this expression. So this is how we can create rejects to match the date of the format dd slash mm slash yyy. Again this one is also simple. Now let us move to the next demo.