How to extract a group from a Java String that contains a Regex patternimport java.util.regex.Matcher; import java.util.regex.Pattern; public class RegexTest {    public static void main(String[] args) {       Pattern pattern = Pattern.compile("fun");       Matcher matcher = pattern.matcher("Java is fun");       // using Matcher find(), group(), start() and end() methods       while (matcher.find()) {          System.out.println("Found the text \"" + matcher.group()             + "\" starting at " + matcher.start()             + " index and ending at index ... Read More

Exampleimport java.util.regex.*; class PatternMatcher {    public static void main(String args[]) {       int count = 0;       // String to be scanned to find the pattern.       String content = "aaa bb aaa";       String string = "aaa";       // Create a Pattern object       Pattern p = Pattern.compile(string);       // get a matcher object       Matcher m = p.matcher(content);       while(m.find()) {          count++;          System.out.println("Match no:"+count);         ... Read More

Java provides the java.util.regex package for pattern matching with regular expressions. Java regular expressions are very similar to the Perl programming language and very easy to learn.A regular expression is a special sequence of characters that help you match or find other strings or sets of strings, using a specialized syntax held in a pattern. They can be used to search, edit, or manipulate text and data.The replaceFirst() and replaceAll() methods replace the text that matches a given regular expression. As their names indicate, replaceFirst replaces the first occurrence, and replaceAll replaces all occurrences.ExampleLive Demoimport java.util.regex.Matcher; import java.util.regex.Pattern; public class RegexMatches { ... Read More

Following is a simple program demonstrating how to use regular expression in Java. Java Regex Characters

Java Regex Capturing Groups

Java Regex Capturing Groups

Capturing groups are a way to treat multiple characters as a single unit. They are created by placing the characters to be grouped inside a set of parentheses. For example, the regular expression (dog) creates a single group containing the letters "d", "o", and "g".Capturing groups are numbered by counting their opening parentheses from the left to the right.In the expression ((A)(B(C))), for example, there are four such groups -((A)(B(C)))(A)(B(C))(C)Back references allow repeating a capturing group using a number like \# where # is the groupnumber. See the example below −ExampleLive Demoimport java.util.regex.Matcher; import java.util.regex.Pattern; public class Tester {   ... Read More

https://www.tutorialspoint.com/javaregex/javaregex_capturing_groups.htm

ExampleLive Demoimport java.util.regex.Matcher; import java.util.regex.Pattern; public class NoRegTest {    public static void main(String[] args) {       String s="^fun";       Pattern pattern = Pattern.compile(s);       Matcher matcher = pattern.matcher("Java is fun");       if(!matcher.find()) {          System.out.println("not found");       }    } }Outputnot found

Exampleimport java.util.regex.*; class PatternMatch{    public static void main(String args[]) {       String content = "I am a student";       String string = ".*boy.*";       boolean isMatch = Pattern.matches(string, content);       System.out.println("The line contains 'boy'?"+ isMatch);    } }Outputthe line contains 'boy'?falsematches()­­It is used to check if the whole text matches a pattern. Its output is boolean. It returns true if match is found otherwise false.This is one of simplest and easiest way of searching a String in a text using Regex .There is a another method compile() , if you want ... Read More