Creating regex to extract 4 digit number from string using java

Question

Hi I am trying to build one regex to extract 4 digit number from given string using java. I tried it in following ways:

String mydata = \"get the 0025 data f         


        

Answer 1

Pattern pattern = Pattern.compile("\\b[0-9]+\\b");

This should do it for you.^$ will compare with the whole string.It will match string with only numbers.

Answer 2

You can go with \d{4} or [0-9]{4} but note that by specifying the ^ at the beginning of regex and $ at the end you're limiting yourself to strings that contain only 4 digits.

My recomendation: Learn some regex basics.

Answer 3

Change you pattern to:

Pattern pattern = Pattern.compile("(\\d{4})");

\d is for a digit and the number in {} is the number of digits you want to have.

Answer 4

If you want to match any number of digits then use pattern like the following:

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

And for exactly 4 digits go for

^\D*(\d{4})\D*$

Answer 5

If you want to end up with 0025,

String mydata = "get the 0025 data from string";
mydata = mydata.replaceAll("\\D", ""); // Replace all non-digits

Answer 6

Remove the anchors.. put paranthesis if you want them in group 1:

Pattern pattern = Pattern.compile("([0-9]+)");   //"[0-9]{4}" for 4 digit number

And extract out matcher.group(1)