Partial match for regular expression in Java

Question

How can I understand if a regex partially matches its subject?

I tried this:

Pattern.compile("^\\d").matcher("01L").hitEnd()

and this:

Pattern.compile("^\\d").matcher("01L").matches()

and they are both false, I want to test if the string starts with a digit.

Answer 1

Use matcher.find() method:

boolean valid = Pattern.compile("^\\d").matcher("01L").find(); //true

PS: If you're using find in a loop or multiple times it is better to do:

Pattern p = Pattern.compile("^\\d"); // outside loop
boolean valid = p.matcher("01L").find(); // repeat calls

You are getting:

• matches attempts to match the entire input against the pattern hence it returns false .
• hitEnd returns true if the end of input was hit by the search engine in the last match operation performed by this matcher and since it didn't you get false