In this chapter, we covered the core constructs of regular expressions in depth. You learned anchors, quantifiers, boundary matchers, various character classes, negated character classes, and predefined character classes. We found out that escaped characters need to be escaped twice in the Java language. You also learned Unicode text matching using regular expressions in Java. We covered greedy, non-greedy, and possessive quantifiers. You learned embedded mode modifiers in Java regular expressions and how they can change the interpretation of a regular expression.

In the next chapter, we will cover another very important feature of regular expressions, called grouping. You will learn the various types of grouping available in Java regular expressions and how to use them.