Java Regex Cheat Sheet

With this, we come to an end of Java String Cheat Sheet. Check out the Java Training by Edureka, a trusted online learning company with a network of more than 250,000 satisfied learners spread across the globe. Edureka’s Java, J2EE & SOA Certification Training is designed for students and professionals who want to be a Java Developer. Regular expression syntax cheatsheet This page provides an overall cheat sheet of all the capabilities of RegExp syntax by aggregating the content of the articles in the RegExp guide. If you need more information on a specific topic, please follow the link on the corresponding heading to access the full article or head to the guide. Regular Expressions Cheat Sheet for Python, PHP, Perl, JavaScript and Ruby developers. The list of the most important metacharacters you'll ever need. Groovy’s basic types; Type Literals Notes; java.lang.String 'hi', 'hi', /hi/, $/hi/$ Double quotes allow embedded expressions. Slashes mean you don’t need to escape characters, the dollar slashes mean you don’t need to escape / characters (good for regular expressions).

Java Regex Cheat Sheet Pdf
Java Design Pattern Cheat Sheet

The Java Regex or Regular Expression is an API to define a pattern for searching or manipulating strings.

It is widely used to define the constraint on strings such as password and email validation. After learning Java regex tutorial, you will be able to test your regular expressions by the Java Regex Tester Tool.

Java Regex API provides 1 interface and 3 classes in java.util.regex package.

java.util.regex package

The Matcher and Pattern classes provide the facility of Java regular expression. The java.util.regex package provides following classes and interfaces for regular expressions.

MatchResult interface
Matcher class
Pattern class
PatternSyntaxException class

Matcher class

It implements the MatchResult interface. It is a regex engine which is used to perform match operations on a character sequence.

No.	Method	Description
1	boolean matches()	test whether the regular expression matches the pattern.
2	boolean find()	finds the next expression that matches the pattern.
3	boolean find(int start)	finds the next expression that matches the pattern from the given start number.
4	String group()	returns the matched subsequence.
5	int start()	returns the starting index of the matched subsequence.
6	int end()	returns the ending index of the matched subsequence.
7	int groupCount()	returns the total number of the matched subsequence.

Pattern class

It is the compiled version of a regular expression. It is used to define a pattern for the regex engine.

No.	Method	Description
1	static Pattern compile(String regex)	compiles the given regex and returns the instance of the Pattern.
2	Matcher matcher(CharSequence input)	creates a matcher that matches the given input with the pattern.
3	static boolean matches(String regex, CharSequence input)	It works as the combination of compile and matcher methods. It compiles the regular expression and matches the given input with the pattern.
4	String[] split(CharSequence input)	splits the given input string around matches of given pattern.
5	String pattern()	returns the regex pattern.

Java Regex Cheat Sheet Pdf

Example of Java Regular Expressions

There are three ways to write the regex example in Java.

Java Design Pattern Cheat Sheet

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Output

Regular Expression . Example

The . (dot) represents a single character.

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Regex Character classes

No.	Character Class	Description
1	[abc]	a, b, or c (simple class)
2	[^abc]	Any character except a, b, or c (negation)
3	[a-zA-Z]	a through z or A through Z, inclusive (range)
4	[a-d[m-p]]	a through d, or m through p: [a-dm-p] (union)
5	[a-z&&[def]]	d, e, or f (intersection)
6	[a-z&&[^bc]]	a through z, except for b and c: [ad-z] (subtraction)
7	[a-z&&[^m-p]]	a through z, and not m through p: [a-lq-z](subtraction)

Regular Expression Character classes Example

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Regex Quantifiers

The quantifiers specify the number of occurrences of a character.

Regex	Description
X?	X occurs once or not at all
X+	X occurs once or more times
X*	X occurs zero or more times
X{n}	X occurs n times only
X{n,}	X occurs n or more times
X{y,z}	X occurs at least y times but less than z times

Regular Expression Character classes and Quantifiers Example

import java.util.regex.*;class RegexExample4{public static void main(String args[]){System.out.println('? quantifier ....');System.out.println(Pattern.matches('[amn]?', 'a'));//true (a or m or n comes one time)System.out.println(Pattern.matches('[amn]?', 'aaa'));//false (a comes more than one time)System.out.println(Pattern.matches('[amn]?', 'aammmnn'));//false (a m and n comes more than one time)System.out.println(Pattern.matches('[amn]?', 'aazzta'));//false (a comes more than one time)System.out.println(Pattern.matches('[amn]?', 'am'));//false (a or m or n must come one time)System.out.println('+ quantifier ....');System.out.println(Pattern.matches('[amn]+', 'a'));//true (a or m or n once or more times)System.out.println(Pattern.matches('[amn]+', 'aaa'));//true (a comes more than one time)System.out.println(Pattern.matches('[amn]+', 'aammmnn'));//true (a or m or n comes more than once)System.out.println(Pattern.matches('[amn]+', 'aazzta'));//false (z and t are not matching pattern)System.out.println('* quantifier ....');System.out.println(Pattern.matches('[amn]*', 'ammmna'));//true (a or m or n may come zero or more times)}}

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Regex Metacharacters

The regular expression metacharacters work as shortcodes.

Regex	Description
.	Any character (may or may not match terminator)
d	Any digits, short of [0-9]
D	Any non-digit, short for [^0-9]
s	Any whitespace character, short for [tnx0Bfr]
S	Any non-whitespace character, short for [^s]
w	Any word character, short for [a-zA-Z_0-9]
W	Any non-word character, short for [^w]
b	A word boundary
B	A non word boundary

Regular Expression Metacharacters Example

import java.util.regex.*;class RegexExample5{public static void main(String args[]){System.out.println('metacharacters d....');d means digitSystem.out.println(Pattern.matches('d', 'abc'));//false (non-digit)System.out.println(Pattern.matches('d', '1'));//true (digit and comes once)System.out.println(Pattern.matches('d', '4443'));//false (digit but comes more than once)System.out.println(Pattern.matches('d', '323abc'));//false (digit and char)System.out.println('metacharacters D....');D means non-digitSystem.out.println(Pattern.matches('D', 'abc'));//false (non-digit but comes more than once)System.out.println(Pattern.matches('D', '1'));//false (digit)System.out.println(Pattern.matches('D', '4443'));//false (digit)System.out.println(Pattern.matches('D', '323abc'));//false (digit and char)System.out.println(Pattern.matches('D', 'm'));//true (non-digit and comes once)System.out.println('metacharacters D with quantifier....');System.out.println(Pattern.matches('D*', 'mak'));//true (non-digit and may come 0 or more times)}}

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Regular Expression Question 1

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Regular Expression Question 2

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Java Regex Finder Example

Output:

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