How to match beginning of line java

Question

I am completely new to regular expressions in java,

I am reading a file line by line and trying to use string.matches for 3 characters and then 10 numbers at the beginning of the line.

In textpad I can do something like:

^[A-Z][A-Z][A-Z][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9]

How do I convert this in to java regex?

Answer 1

You have to use quantifiers. So,

x{n} means match n number of x exactly

x{n,} matches x n to many times

x{n,m} matches x n to m times..

So,your regex would be

^[a-zA-Z]{3}\\d{10}

Answer 2

it's same, but optimized:

"^[A-Z]{3}[0-9]{10}"

or equal one

"^[A-Z]{3}\\d{10}"

Answer 3

You can use the method string.startsWith(). Then the first '^' is not needed.