Multiple spaces in a regular expression can make it hard to tell how many spaces should be matched. It’s more readable to use only one space and then indicate with a quantifier how many spaces are expected.

Noncompliant Code Example

Pattern.compile("hello   world");

Compliant Solution

Pattern.compile("hello {3}world");

Exceptions

In free-spacing mode (Pattern.COMMENTS flag, or with embedded flag expression (?x)), whitespaces are ignored. In this case no issue should be triggered, because the whitespaces may be intended to improve readability.