import java.util.regex.*;  

public class RegexExample1{  

public static void main(String args[]){  

//1st way  

Pattern p = Pattern.compile(".s");//. represents single character  

Matcher m = p.matcher("as");  

boolean b = m.matches();  

//2nd way  

boolean b2=Pattern.compile(".s").matcher("as").matches();  

//3rd way  

boolean b3 = Pattern.matches(".s", "as");  

System.out.println(b+" "+b2+" "+b3);  

}}  

/*

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

or manipulating strings.

*/

​

// Regex Character classes

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)

​

Please click source link for more details

​

​

​

package RegexMainNMD;

//NMD

import java.util.regex.Matcher;

import java.util.regex.Pattern;

​

public class RegexNMDSE {

    public static void main(String[] args) {

        String strTest = "Regex 15-05-2020, Nguyen Minh Duc 16/02/1998. Deadline 18_02_2020";

        Pattern patternDate = Pattern.compile("\\d{2}[-|/]\\d{2}[-|/]\\d{4}");

        Matcher matcher = patternDate.matcher(strTest);

        System.out.println("Ngày tháng năm trong chuỗi đầu vào: " + strTest +" là:");

        while(matcher.find()) {

            System.out.println(strTest.substring(matcher.start(), matcher.end()));

        }         

        String strTest2 = "15/05/2020";

        String strTest3 = "16/02/mdse";

        patternDate = Pattern.compile("^\\d{2}[-|/]\\d{2}[-|/]\\d{4}$");

        System.out.println("Chuỗi " + strTest2 + " có định dạng ngày tháng: "

                + patternDate.matcher(strTest2).matches());

        System.out.println("Chuỗi " + strTest3 + " có định dạng ngày tháng: "

                + patternDate.matcher(strTest3).matches());

    } 

}

import java.util.regex.Matcher;

import java.util.regex.Pattern;

​

public class Main 

{

 public static void main(String[] args) 

 {

  Pattern pattern = Pattern.compile("Alex|Brian");

  Matcher matcher = pattern.matcher("Generally, Alex and Brian share a great bonding.");

  while (matcher.find()) {

            System.out.print("Start index: " + matcher.start());

            System.out.print(" End index: " + matcher.end() + " ");

            System.out.println(" - " + matcher.group());

        }

 }

}

Pattern pattern = Pattern.compile("1");

Matcher matcher = pattern.matcher("111");

while (matcher.find()) {

    System.out.println(matcher.group());

}

import java.util.regex.Matcher;

import java.util.regex.Pattern;

​

public class Main {

  public static void main(String[] args) {

    Pattern pattern = Pattern.compile("w3schools", Pattern.CASE_INSENSITIVE);

    Matcher matcher = pattern.matcher("Visit W3Schools!");

    boolean matchFound = matcher.find();

    if(matchFound) {

      System.out.println("Match found");

    } else {

      System.out.println("Match not found");

    }

  }

}

// Outputs Match found

import java.io.*;

import java.util.regex.*;

​

public class testRegex {

​

    private static Pattern pattern;

    private static Matcher matcher;

​

    public static void main(String args[]) {

        pattern = Pattern.compile("Hugo");

        matcher = pattern.matcher("Hugo Etiévant");

        while(matcher.find()) {

            System.out.println("Trouvé !");

        }

    }

}

//Ther are three type of REGULAR EXPRESSION     

   //first

   ^(.+)@(.+)$   "^(.+)@(.+)$\""

   //second

   ^[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,6}$

     //third

   ^[\\w!#$%&'*+/=?`{|}~^-]+(?:\\.[\\w!#$%&'*+/=?`{|}~^-]+)*@(?!-)(?:[a-zA-Z0-9-]+\\.)+[a-zA-Z]{2,6}$