😭 java

Question

5. Write a regular expression that determines whether the given string is a hexadecimal color identifier in HTML. Where #FFFFFF is for white, #000000 for black, #FF0000 for red, etc. – an example of correct expressions: #FFFFFF, #FF3421, #00ff00. – an example of incorrect expressions: 232323, f#fddee, #fd2.

Answer 1

Try to describe the expression in words before jumping to regex.

The string always starts with '#'.

There are 6 possible values after the '#'.

Each of those values are from 0 to 9 or a to f.

Those values can also be capitalized A to F.

Here is my regex:
^#[0-9a-fA-F]{6}$

^ start of the string (might be optional)
[0-9] being from 0 to 9
[a-fA-F] being from a to f and A to F
{6} repeat 6 times
$ end of the string (might be optional)

Last note, regex is not specific to Java it is a powerful tool that is being used across multiple languages, almost everywhere!
I recommend you to look into https://regex101.com it's a great site to help with regex.

I hope this helps :)