Regular Expressions
Introduction
Regular expressions in Java are useful for searching, editing and manipulating strings. Regular Expressions are also known as Regex.
Java Regex provides three classes in java.util.regex package:
- Matcher
— Used for defining the String pattern to match - Pattern
— Used for peforning math on given pattern - PatternSyntaxException
— Used for indicate exceptions in the pattern
RegEx Example:
- Check that the string contains only characters and no numbers or special characters.
import java.util.regex.*;
public class RegExExample {
public static final String ARTICLE_STRING = "Codevarsity";
public static void main(String[] args) {
Pattern pattern = Pattern.compile("^[a-zA-Z]*$");
Matcher match = pattern.matcher(ARTICLE_STRING);
boolean result = match.matches();
System.out.println("Result: " + result);
}
}
Result: true
Understanding the pattern:
"^[a-zA-Z]*$"
^ – The beginning of a line
[a-zA-Z] – Match characters from a-z and A-Z
*$ – The end of the line
RegEx Cheatsheet:
- Here is a very good link to RegEx Cheatsheet