Regex to test if a string ends with a number

Question

I'd like to test if a string ends with a a digit. I expect the following Java line to print true. Why does it print false?

System.out.println("I end with a number 4".matches("\\d$"));

Answer 1

In Java Regex, there's a difference between Matcher.find() (find a match anywhere in the String) and Matcher.matches() (match the entire String).

String only has a matches() method (implemented equivalent to this code:Pattern.compile(pattern).matcher(this).matches();), so you need to create a pattern that matches the full String:

System.out.println("I end with a number 4".matches("^.*\\d$"));

Answer 2

Your regex will not match the entire string but only the last part. Try the below code and it should work fine as it matches the entire string.

System.out.println("I end with a number 4".matches("^.+?\\d$"));

You can test this for a quick check on online regex testers like this one: http://www.regexplanet.com/simple/index.html. This also gives you what you should use in the Java code in the results with appropriate escapes.

The .+ will ensure that there is atleast one character before the digit. The ? will ensure it does a lazy match instead of a greedy match.