Java Regex Syntax

In this article we want to talk about Java Regex Syntax, Java is popular programming language used for building different types of applications. and one of the features that Java has is support for regular expressions also we can call it regex. Regular expressions are a powerful way to match, search and manipulate text. in this article we want to talk about the syntax of Java regex, including different characters and symbols that is used for creating patterns and matching the text.



Java Regex Syntax

We can say that regular expression is simply a pattern of characters that matches a specific sequence of text. in Java we can use the Pattern class to create a regular expression pattern. after that we can use this pattern to search, match or replace text.



This is a simple example of regular expression pattern in Java, this pattern matches the string hello exactly. you can use this pattern to search for instances of hello in a larger string like this:



This is another example, in here the Matcher class represents a matcher for a particular pattern, and you can use it to search for matches in a string. in this case find() method returns true because the string hello is found in the larger string hello world.



Characters and Symbols

. dot Matches any single character except a line break.
* Matches zero or more occurrences of the preceding character or group.
+ Matches one or more occurrences of the preceding character or group.
? Matches zero or one occurrences of the preceding character or group.
[] Matches any one character from the set of characters inside the brackets. For example, [abc] matches either “a”, “b”, or “c”.
^ Matches the beginning of a line.
$ Matches the end of a line.
| Matches either the expression before or after the symbol. For example, a|b matches either “a” or “b”.
() Groups expressions together.



These are a few examples of how these characters and symbols can be used in regular expressions.



This is a complete Java code example that demonstrates how to use regular expressions to validate an email address, in this example we have defined a regular expression pattern EMAIL_REGEX that matches valid email addresses. after that we have defined a static method validateEmail that takes an email address as a parameter, compiles the pattern and matches it against the email address using Matcher object. this method returns true if the email address matches the pattern, and it indicates that it is a valid email address, otherwise it will say false, it means that email address is not valid.




Run the code this will be the result

Java Regex Syntax
Java Regex Syntax



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