How to use predefined character class whitespace and non-whitespace | Java Regex | Regex in java

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https://www.youtube.com/watch?v=9DuMFjsx0gA&list=UUhwKlOVR041tngjerWxVccw

RegexDemo.java

import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 *
 * Predefined Character Classes
 *
 * The Java regex API also accepts predefined character classes.One
 * special aspect of the Java version of this regex is the escape
 * character.
 *
 * As we will see, most characters will start with a backslash, which
 * has a special meaning in Java. For these to be compiled by the
 * Pattern class – the leading backslash must be escaped i.e. \s
 * becomes \\s.
 *
 */
public class RegexDemo
{

    public static void main(String[] args)
    {
        /*
         * Matching white space:
         */
        calculateMatches("\\s", "a    c");
        /*
         * Matching non-white space:
         */
        calculateMatches("\\S", "a    c");
    }

    private static void calculateMatches(String regex, String inputText)
    {
        Pattern pattern = Pattern.compile(regex);
        Matcher matcher = pattern.matcher(inputText);
        int matches = 0;

        /*
         * The find method keeps advancing through the input text and
         * returns true for every match, so we can use it to find the
         * match count as well:
         */
        while (matcher.find())
        {
            ++matches;
        }
        System.out.println("Number of Matches = " + matches);
    }

}

Output

Number of Matches = 4
Number of Matches = 2

Click the below link to download the code:
https://sites.google.com/site/ramj2eev1/home/javabasics/RegexDemo_predefined_class_s_S.zip?attredirects=0&d=1

Github Link:
https://github.com/ramram43210/Java/tree/master/BasicJava/RegexDemo_predefined_class_s_S

Bitbucket Link:
https://bitbucket.org/ramram43210/java/src/9ca0aed85cf523c7d53f60f93dd6c7d098a3db63/BasicJava/RegexDemo_predefined_class_s_S/?at=master

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How to use predefined character class digit and non-digit | Java Regex | Regex in java

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https://www.youtube.com/watch?v=N6c5A_m68q4&list=UUhwKlOVR041tngjerWxVccw

RegexDemo.java

import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 *
 * Predefined Character Classes
 *
 * The Java regex API also accepts predefined character classes.One
 * special aspect of the Java version of this regex is the escape
 * character.
 *
 * As we will see, most characters will start with a backslash, which
 * has a special meaning in Java. For these to be compiled by the
 * Pattern class – the leading backslash must be escaped i.e. \d
 * becomes \\d.
 *
 */
public class RegexDemo
{

    public static void main(String[] args)
    {
        /*
         * Matching digits, equivalent to [0-9]:
         */
        calculateMatches("\\d", "12abcd");
        /*
         * Matching non-digits, equivalent to [^0-9]:
         */
        calculateMatches("\\D", "12abcd");
    }

    private static void calculateMatches(String regex, String inputText)
    {
        Pattern pattern = Pattern.compile(regex);
        Matcher matcher = pattern.matcher(inputText);
        int matches = 0;

        /*
         * The find method keeps advancing through the input text and
         * returns true for every match, so we can use it to find the
         * match count as well:
         */
        while (matcher.find())
        {
            ++matches;
        }
        System.out.println("Number of Matches = " + matches);
    }

}

Output

Number of Matches = 2
Number of Matches = 4

Click the below link to download the code:
https://sites.google.com/site/ramj2eev1/home/javabasics/RegexDemo_predefined_class_d_D.zip?attredirects=0&d=1

Github Link:
https://github.com/ramram43210/Java/tree/master/BasicJava/RegexDemo_predefined_class_d_D

Bitbucket Link:
https://bitbucket.org/ramram43210/java/src/9ca0aed85cf523c7d53f60f93dd6c7d098a3db63/BasicJava/RegexDemo_predefined_class_d_D/?at=master

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How to use Metacharacter subtraction class | Java Regex | Java Regular Expressions | Regex in java

Click here to watch on Youtube : 
https://www.youtube.com/watch?v=8rW3y46GkN8&list=UUhwKlOVR041tngjerWxVccw

RegexDemo.java

import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 *
 * Subtraction Class
 *
 */
public class RegexDemo
{

    public static void main(String[] args)
    {
        /*
         * We will get 8 matches because the Subtraction of the two
         * sets has only 8 elements.
         */
        calculateMatches("[0-9&&[^12]]", "0123456789");
        calculateMatches("[0-9&&[^12]]", "123");
    }

    private static void calculateMatches(String regex, String inputText)
    {
        Pattern pattern = Pattern.compile(regex);
        Matcher matcher = pattern.matcher(inputText);
        int matches = 0;

        /*
         * The find method keeps advancing through the input text and
         * returns true for every match, so we can use it to find the
         * match count as well:
         */
        while (matcher.find())
        {
            ++matches;
        }
        System.out.println("Number of Matches = " + matches);
    }

}

Output

Number of Matches = 8
Number of Matches = 1

Click the below link to download the code:
https://sites.google.com/site/ramj2eev1/home/javabasics/RegexDemo_substraction_class.zip?attredirects=0&d=1

Github Link:
https://github.com/ramram43210/Java/tree/master/BasicJava/RegexDemo_substraction_class

Bitbucket Link:
https://bitbucket.org/ramram43210/java/src/9ca0aed85cf523c7d53f60f93dd6c7d098a3db63/BasicJava/RegexDemo_substraction_class/?at=master

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How to use Metacharacter Intersection class | Java Regex | Java Regular Expressions | Regex in java

Click here to watch on Youtube :
https://www.youtube.com/watch?v=7H4yAVbg3-Y&list=UUhwKlOVR041tngjerWxVccw

RegexDemo.java

import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 *
 * Intersection Class
 *
 */
public class RegexDemo
{

    public static void main(String[] args)
    {
        /*
         * We will get 4 matches because the intersection of the two
         * sets has only 4 elements[3456].
         */
        calculateMatches("[1-6&&[3-9]]", "3456");
        calculateMatches("[1-6&&[3-9]]", "123456789");
    }

    private static void calculateMatches(String regex, String inputText)
    {
        Pattern pattern = Pattern.compile(regex);
        Matcher matcher = pattern.matcher(inputText);
        int matches = 0;

        /*
         * The find method keeps advancing through the input text and
         * returns true for every match, so we can use it to find the
         * match count as well:
         */
        while (matcher.find())
        {
            ++matches;
        }
        System.out.println("Number of Matches = " + matches);
    }

}

Output

Number of Matches = 4
Number of Matches = 4

Click the below link to download the code:
https://sites.google.com/site/ramj2eev1/home/javabasics/RegexDemo_intersection_class.zip?attredirects=0&d=1

Github Link:
https://github.com/ramram43210/Java/tree/master/BasicJava/RegexDemo_intersection_class

Bitbucket Link:
https://bitbucket.org/ramram43210/java/src/9ca0aed85cf523c7d53f60f93dd6c7d098a3db63/BasicJava/RegexDemo_intersection_class/?at=master

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How to use Metacharacter Union class | Java Regex | Java Regular Expressions | Regex in java

Click here to watch on Youtube : 
https://www.youtube.com/watch?v=Y6aSPM9OYDo&list=UUhwKlOVR041tngjerWxVccw

RegexDemo.java

import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 *
 * Union Class
 *
 */
public class RegexDemo
{

    public static void main(String[] args)
    {
        /*
         * This will only match 6 out of the 9 integers because the
         * union set skips  4,5 and 6.
         */
        calculateMatches("[1-3[7-9]]", "123456789");
    }

    private static void calculateMatches(String regex, String inputText)
    {
        Pattern pattern = Pattern.compile(regex);
        Matcher matcher = pattern.matcher(inputText);
        int matches = 0;

        /*
         * The find method keeps advancing through the input text and
         * returns true for every match, so we can use it to find the
         * match count as well:
         */
        while (matcher.find())
        {
            ++matches;
        }
        System.out.println("Number of Matches = " + matches);
    }

}

Output

Number of Matches = 6

Click the below link to download the code:
https://sites.google.com/site/ramj2eev1/home/javabasics/RegexDemo_union_class.zip?attredirects=0&d=1

Github Link:
https://github.com/ramram43210/Java/tree/master/BasicJava/RegexDemo_union_class

Bitbucket Link:
https://bitbucket.org/ramram43210/java/src/57d5e7f2c5fabff367c40b36a92925e1158e7f5a/BasicJava/RegexDemo_union_class/?at=master

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How to use Metacharacter Range class | Java Regex | Java Regular Expressions | Regex in java

Click here to watch on Youtube : 
https://www.youtube.com/watch?v=vPCccRyUXvU&list=UUhwKlOVR041tngjerWxVccw

RegexDemo.java

import java.util.regex.Matcher;
import java.util.regex.Pattern;
/**
 *
 * Range Class Example
 *
 */
public class RegexDemo
{

    public static void main(String[] args)
    {
        /*
         * Matching uppercase letters:
         */
        calculateMatches( "[A-Z]", "Welcome To India");
        /*
         * Matching lowercase letters:
         */
        calculateMatches( "[a-z]", "Two");
        /*
         * Matching both upper case and lower case letters:
         */
        calculateMatches("[a-zA-Z]", "Two");
        /*
         * Matching a given range of numbers:
         */
        calculateMatches( "[1-5]", "hi 65");
       
    }

    private static void calculateMatches(String regex, String inputText)
    {
        Pattern pattern = Pattern.compile(regex);
        Matcher matcher = pattern.matcher(inputText);
        int matches = 0;

        /*
         * The find method keeps advancing through the input text and
         * returns true for every match, so we can use it to find the
         * match count as well:
         */
        while (matcher.find())
        {
            ++matches;
        }
        System.out.println("Number of Matches = " + matches);
    }

}

Output

Number of Matches = 3
Number of Matches = 2
Number of Matches = 3
Number of Matches = 1

Click the below link to download the code:
https://sites.google.com/site/ramj2eev1/home/javabasics/RegexDemo_metachar_range_class.zip?attredirects=0&d=1

Github Link:
https://github.com/ramram43210/Java/tree/master/BasicJava/RegexDemo_metachar_range_class

Bitbucket Link:
https://bitbucket.org/ramram43210/java/src/57d5e7f2c5fabff367c40b36a92925e1158e7f5a/BasicJava/RegexDemo_metachar_range_class/?at=master

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How to use Metacharacter NOR class | Java Regex | Java Regular Expressions | Regex in java

Click here to watch on Youtube : 
https://www.youtube.com/watch?v=3Sc1buVwCXg&list=UUhwKlOVR041tngjerWxVccw

RegexDemo.java

import java.util.regex.Matcher;
import java.util.regex.Pattern;
/**
 *
 * NOR Class Example
 *
 */
public class RegexDemo
{

    public static void main(String[] args)
    {
        calculateMatches("[^abc]", "z");
        calculateMatches("[^bcr]at", "sat mat");
        calculateMatches("[^bcr]at", "sat mat eat bat cat");
    }

    private static void calculateMatches(String regex, String inputText)
    {
        Pattern pattern = Pattern.compile(regex);
        Matcher matcher = pattern.matcher(inputText);
        int matches = 0;

        /*
         * The find method keeps advancing through the input text and
         * returns true for every match, so we can use it to find the
         * match count as well:
         */
        while (matcher.find())
        {
            ++matches;
        }
        System.out.println("Number of Matches = " + matches);
    }

}

Output

Number of Matches = 1
Number of Matches = 2
Number of Matches = 3

Click the below link to download the code:
https://sites.google.com/site/ramj2eev1/home/javabasics/RegexDemo_metachar_nor_class.zip?attredirects=0&d=1

Github Link:
https://github.com/ramram43210/Java/tree/master/BasicJava/RegexDemo_metachar_nor_class

Bitbucket Link:
https://bitbucket.org/ramram43210/java/src/57d5e7f2c5fabff367c40b36a92925e1158e7f5a/BasicJava/RegexDemo_metachar_nor_class/?at=master

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How to use metacharacter OR class | Java Regex | Java Regular Expressions | Regex in java

Click here to watch on Youtube : 
https://www.youtube.com/watch?v=kA9rnZ5eubU&list=UUhwKlOVR041tngjerWxVccw

RegexDemo.java

import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * OR Class Example
 */
public class RegexDemo
{

    public static void main(String[] args)
    {
        /*
         * [abc] - Any of the elements in the set is matched
         */
        calculateMatches("[abc]", "b");
        calculateMatches("[abc]", "cab");
        calculateMatches("[abc]", "caABZ9");

        /*
         * They can also be alternated as part of a String. In the
         * following example, when we create different words by
         * alternating the first letter with each element of the set,
         * they are all matched:
         */
        calculateMatches("[bcr]at", "bat cat rat zat");

    }

    private static void calculateMatches(String regex, String inputText)
    {
        Pattern pattern = Pattern.compile(regex);
        Matcher matcher = pattern.matcher(inputText);
        int matches = 0;

        /*
         * The find method keeps advancing through the input text and
         * returns true for every match, so we can use it to find the
         * match count as well:
         */
        while (matcher.find())
        {
            ++matches;
        }
        System.out.println("Number of Matches = " + matches);
    }

}

Output

Number of Matches = 1
Number of Matches = 3
Number of Matches = 2
Number of Matches = 3

Click the below link to download the code:
https://sites.google.com/site/ramj2eev1/home/javabasics/RegexDemo_metachar_or_class.zip?attredirects=0&d=1

Github Link:
https://github.com/ramram43210/Java/tree/master/BasicJava/RegexDemo_metachar_or_class

Bitbucket Link:
https://bitbucket.org/ramram43210/java/src/57d5e7f2c5fabff367c40b36a92925e1158e7f5a/BasicJava/RegexDemo_metachar_or_class/?at=master

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How to use Metacharacter dot | Java Regex | Java Regular Expressions | Regex in java

Click here to watch on Youtube : 
https://www.youtube.com/watch?v=bOl4sDJfeAU&list=UUhwKlOVR041tngjerWxVccw

RegexDemo.java

import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * Meta Characters example
 */
public class RegexDemo
{

    public static void main(String[] args)
    {
        /*
         * Meta characters affect the way a pattern is matched, in a
         * way adding logic to the search pattern. The Java API
         * supports several metacharacters, the most straightforward
         * being the dot “." which matches any character:
         */
        calculateMatches(".", "foofoo");
        /*
         * Notice the dot after the foo in the regex. The matcher
         * matches every text that is preceded by foo since the last
         * dot part means any character after. So after finding the
         * first foo, the rest is seen as any character. That is why
         * there is only a single match.
         */
        calculateMatches("foo.", "foofoo");
    }

    private static void calculateMatches(String regex, String inputText)
    {
        Pattern pattern = Pattern.compile(regex);
        Matcher matcher = pattern.matcher(inputText);
        int matches = 0;

        /*
         * The find method keeps advancing through the input text and
         * returns true for every match, so we can use it to find the
         * match count as well:
         */
        while (matcher.find())
        {
            ++matches;
        }
        System.out.println("Number of Matches = " + matches);
    }

}

Output

Number of Matches = 6
Number of Matches = 1

Click the below link to download the code:
https://sites.google.com/site/ramj2eev1/home/javabasics/RegexDemo_metachar_dot_cal.zip?attredirects=0&d=1

Github Link:
https://github.com/ramram43210/Java/tree/master/BasicJava/RegexDemo_metachar_dot_cal

Bitbucket Link:
https://bitbucket.org/ramram43210/java/src/57d5e7f2c5fabff367c40b36a92925e1158e7f5a/BasicJava/RegexDemo_metachar_dot_cal/?at=master

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How to calculate how many times foo is there in the input text | Regex in java

Click here to watch on Youtube : 
https://www.youtube.com/watch?v=lZFRN0LomMY&list=UUhwKlOVR041tngjerWxVccw

RegexDemo.java

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class RegexDemo
{

    public static void main(String[] args)
    {
        calculateMatches("foo", "foo come foo");
    }

    private static void calculateMatches(String regex, String inputText)
    {
        Pattern pattern = Pattern.compile(regex);
        Matcher matcher = pattern.matcher(inputText);
        int matches = 0;

        /*
         * The find method keeps advancing through the input text and
         * returns true for every match, so we can use it to find the
         * match count as well:
         */
        while (matcher.find())
        {
            ++matches;
        }
        System.out.println("Number of Matches = "+matches);
    }

}

Output

Number of Matches = 2

Click the below link to download the code:
https://sites.google.com/site/ramj2eev1/home/javabasics/RegexDemo_calculate_matches.zip?attredirects=0&d=1

Github Link:
https://github.com/ramram43210/Java/tree/master/BasicJava/RegexDemo_calculate_matches

Bitbucket Link:
https://bitbucket.org/ramram43210/java/src/57d5e7f2c5fabff367c40b36a92925e1158e7f5a/BasicJava/RegexDemo_calculate_matches/?at=master

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How to filter list of email addresses using asPredicate method of Pattern class | Regex in java

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https://www.youtube.com/watch?v=mFNZpvYVTkU&list=UUhwKlOVR041tngjerWxVccw

RegexPredicateDemo.java

import java.util.Arrays;
import java.util.List;
import java.util.function.Predicate;
import java.util.regex.Pattern;
import java.util.stream.Collectors;

public class RegexPredicateDemo
{

    public static void main(String[] args)
    {
        String regex = "^(.+)@gmail.com$";
        Pattern pattern = Pattern.compile(regex);

        /*
         * Returns:The predicate which can be used for matching on a
         * string
         */
        Predicate<String> emailFilterPredicate = pattern.asPredicate();

        List<String> emailList = Arrays.asList("peter@yahoo.com",
                "bob@gmail.com", "juli@gmail.com",
                "david@rediff.com");

        /*
         *  Apply predicate filter
         */
        List<String> desiredEmailList = emailList.stream()
                                           .filter(emailFilterPredicate)
                                           .collect(Collectors.<String>toList());

        desiredEmailList.forEach(System.out::println);
    }

}

Output

bob@gmail.com
juli@gmail.com

RegexDemo.java

import java.util.Arrays;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class RegexDemo
{

    public static void main(String[] args)
    {

        String regex = "^(.+)@gmail.com$";
        Pattern pattern = Pattern.compile(regex);

        List<String> emailList = Arrays.asList("peter@yahoo.com",
                "bob@gmail.com", "juli@gmail.com",
                "david@rediff.com");

        for (String email : emailList)
        {
            Matcher matcher = pattern.matcher(email);

            if (matcher.matches())
            {
                System.out.println(email);
            }
        }
    }

}

Output

bob@gmail.com
juli@gmail.com

Click the below link to download the code:
https://sites.google.com/site/ramj2eev1/home/javabasics/RegexDemo_asPredicate.zip?attredirects=0&d=1

Github Link:
https://github.com/ramram43210/Java/tree/master/BasicJava/RegexDemo_asPredicate

Bitbucket Link:
https://bitbucket.org/ramram43210/java/src/57d5e7f2c5fabff367c40b36a92925e1158e7f5a/BasicJava/RegexDemo_asPredicate/?at=master

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