Regular Expressions in Java

Now that you have an idea of how regular expressions can be used to match patterns, this topic will focus on how regular expressions can be used within Java applications. To use regular expressions in Java, the java.util.regex package is available. The two main classes there are called Pattern and Matcher.

The Pattern class handles the actual pattern; it validates, compiles, and returns a Pattern object that you can store and reuse multiple times. It can also be used to perform quick validations against a supplied string.

The Matcher class allows us to extract more information, and to perform different kinds of matching on the supplied text.

Creating a Pattern object is as simple as using the static compile method.

For example, you would like to compile a pattern to ensure that a text contains at least one a. Your Java code should be as follows:

Pattern pattern = Pattern.compile("a+");
Matcher matcher = pattern.matcher("How...