54 lines
1.5 KiB
Markdown
54 lines
1.5 KiB
Markdown
---
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title: Regular Expressions
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---
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# Regular Expressions
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### Introduction
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Regular expressions in Java are useful for searching, editing and manipulating strings. Regular Expressions are also known as Regex.
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### Java Regex provides three classes in java.util.regex package:
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- Matcher
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-- Used for defining the String pattern to match
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- Pattern
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-- Used for peforning math on given pattern
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- PatternSyntaxException
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-- Used for indicate exceptions in the pattern
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### RegEx Example:
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- Check that the string contains only characters and no numbers or special characters.
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```
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import java.util.regex.*;
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public class RegExExample {
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public static final String ARTICLE_STRING = "freecodecamp";
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public static void main(String[] args) {
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Pattern pattern = Pattern.compile("^[a-zA-Z]*$");
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Matcher match = pattern.matcher(ARTICLE_STRING);
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boolean result = match.matches();
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System.out.println("Result: " + result);
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}
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}
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```
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```
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Result: true
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```
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### Understanding the pattern:
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```"^[a-zA-Z]*$"```
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^ - The beginning of a line
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[a-zA-Z] - Match characters from a-z and A-Z
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*$ - The end of the line
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### RegEx Cheatsheet:
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- Here is a very good link to [RegEx Cheatsheet](https://docs.oracle.com/javase/7/docs/api/java/util/regex/Pattern.html)
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#### More Information:
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<!-- Please add any articles you think might be helpful to read before writing the article -->
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- [Class Pattern](https://docs.oracle.com/javase/7/docs/api/java/util/regex/Pattern.html)
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- [Lesson on Regular Expression](https://docs.oracle.com/javase/tutorial/essential/regex/)
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