JAVA EE: What are Java Regular Expressions and how to use pattern class | Java Regex

Tuesday 19 December 2017

What are Java Regular Expressions and how to use pattern class | Java Regex | Regex in java

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What are Java Regular Expressions and how to use pattern class | Java Regex | Regex in java

RegexDemo1.java

import java.util.regex.Pattern;

public class RegexDemo1

{

    public static void main(String[] args)

    {

        String inputCharSeq = "Peter Welcome to India.";

        String regex = ".*Welcome.*";

        /*
         * Parameters:
         * 
         * regex - The expression to be compiled
         * 
         * input - The character sequence to be matched
         * 
         * Returns: 
         * 
         * whether or not the regular expression matches on
         * the input
         * 
         */

        boolean isMatch = Pattern.matches(regex, inputCharSeq);

        System.out.println("The text contains 'Welcome'? = " + isMatch);

    }

}

Output

The text contains 'Welcome'? = true

RegexDemo2.java

import java.util.regex.Matcher;

import java.util.regex.Pattern;



public class RegexDemo2

{



    public static void main(String[] args)

    {

        String inputCharSeq = "Peter Welcome to India.";



        String regex = ".*WElCoMe.*";



        /*
         * Parameters:
         * 
         * regex - The expression to be compiled
         *       * 
         * flags - Match flags, a bit mask that may include
         * CASE_INSENSITIVE, MULTILINE, DOTALL, UNICODE_CASE,
         * CANON_EQ, UNIX_LINES, LITERAL, UNICODE_CHARACTER_CLASS and
         * COMMENTS
         * 
         * Returns:
         * 
         * the given regular expression compiled into a pattern with
         * the given flags
         * 
         */

        Pattern patternObj = Pattern.compile(regex, Pattern.CASE_INSENSITIVE);

        /*
         * Parameters: 
         * 
         * input - The character sequence to be matched
         * 
         * Returns:
         * 
         * A new matcher for this pattern
         */

        Matcher matcher = patternObj.matcher(inputCharSeq);

        /*
         * Returns:true if, and only if, the entire region sequence matches this
         * matcher's pattern
         */

        boolean isMatched = matcher.matches();

        System.out.println("Is it a Match? = " + isMatched);

    }



}