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Explain the Java regular expression construct "re?".

Maruthi Krishna
Maruthi Krishna
Updated on 19-Nov-2019 240 Views

The subexpression/metacharacter “re?” matches 0 or 1 occurrence of the preceding expression.Example 1import java.util.regex.Matcher; import java.util.regex.Pattern; public class RegexExample {    public static void main( String args[] ) {       String regex = "Wel?";       String input = "Welcome to Tutorialspoint";       Pattern p = Pattern.compile(regex);       Matcher m = p.matcher(input);       int count = 0;       while(m.find()) {          count++;       }       System.out.println("Number of matches: "+count);    } }OutputNumber of matches: 1Example 2Following Java program accepts a string from ...

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Explain the Sub-Expression "(?> re)" in Java Regular Expressions

Maruthi Krishna
Maruthi Krishna
Updated on 19-Nov-2019 225 Views

The subexpression/metacharacter “(?> re)” matches the independent pattern without backtracking.Exampleimport java.util.Scanner; import java.util.regex.Matcher; import java.util.regex.Pattern; public class PatternExample {    public static void main(String args[]) {       //Reading String from user       System.out.println("Enter a String");       Scanner sc = new Scanner(System.in);       String input = sc.next();       String regex = "(?>[0-9])";       //Compiling the regular expression       Pattern pattern = Pattern.compile(regex);       //Retrieving the matcher object       Matcher matcher = pattern.matcher(input);       //verifying whether match occurred       boolean ...

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Sub-Expression "(?: re)" in Java Regular Expressions

Maruthi Krishna
Maruthi Krishna
Updated on 19-Nov-2019 235 Views

The subexpression/metacharacter “(?: re)” groups regular expressions without remembering the matched text.Exampleimport java.util.Scanner; import java.util.regex.Matcher; import java.util.regex.Pattern; public class PatternExample {    public static void main(String args[]) {       //Reading String from user       System.out.println("Enter a String");       Scanner sc = new Scanner(System.in);       String input = sc.next();       String regex = "(?:[0-9])";       //Compiling the regular expression       Pattern pattern = Pattern.compile(regex);       //Retrieving the matcher object       Matcher matcher = pattern.matcher(input);       //verifying whether match occurred     ...

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Regular Expression "(re)" Sub-Expression in Java

Maruthi Krishna
Maruthi Krishna
Updated on 19-Nov-2019 402 Views

The subexpression/metacharacter “( )” groups the regular expressions and remembers the matched text.Example 1import java.util.Scanner; import java.util.regex.Matcher; import java.util.regex.Pattern; public class Example {    public static void main( String args[] ) {       String input = "Hello how are you welcome to Tutorialspoint";       String regex = "H(ell|ow)";       //Compiling the regular expression       Pattern pattern = Pattern.compile(regex);       //Retrieving the matcher object       Matcher matcher = pattern.matcher(input);       if(matcher.find()) {          System.out.println("Match found");       } else {       ...

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Explain the Metacharacter "B" in Java Regular Expressions.

Maruthi Krishna
Maruthi Krishna
Updated on 19-Nov-2019 282 Views

The subexpression/metacharacter “\B” matches the non-word boundaries.Example 1import java.util.Scanner; import java.util.regex.Matcher; import java.util.regex.Pattern; public class RegexExample {    public static void main( String args[] ) {       String regex = "\Bcause";       Scanner sc = new Scanner(System.in);       System.out.println("Enter a string: ");       String input = sc.nextLine();       Pattern p = Pattern.compile(regex);       Matcher m = p.matcher(input);       int count = 0;       while(m.find()) {          count ++;       }       System.out.println("Number of matches: "+count);    } ...

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How to match a character from given string including case using Java regex?

Maruthi Krishna
Maruthi Krishna
Updated on 19-Nov-2019 454 Views

The java.util.regex package of java provides various classes to find particular patterns in character sequences. The pattern class of this package is a compiled representation of a regular expression.To match a specific character from the given input string −Get the input string.This compile() method of this class accepts a string value representing a regular expression and an integer value representing a flag returns a Pattern object. Compile the regular expression bypassing −The pattern matcher “[ ]” with required character in it ex: “[t]”.The flag CASE_INSENSITIVE to ignore case.The matcher() method of the Pattern class accepts an input string and returns ...

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How to match word boundaries using Java RegEx?

Maruthi Krishna
Maruthi Krishna
Updated on 19-Nov-2019 557 Views

You can match the word boundaries using the meta character “\b”.Example 1import java.util.Scanner; import java.util.regex.Matcher; import java.util.regex.Pattern; public class Example {    public static void main(String args[]) {       //Reading String from user       System.out.println("Enter a String");       Scanner sc = new Scanner(System.in);       String input = sc.nextLine();       String regex = "\b";       //Compiling the regular expression       Pattern pattern = Pattern.compile(regex);       //Retrieving the matcher object       Matcher matcher = pattern.matcher(input);       int count = 0;     ...

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How to match non-digits using Java Regular Expression (RegEx)

Maruthi Krishna
Maruthi Krishna
Updated on 19-Nov-2019 2K+ Views

You can match non-digit character using the meta character "\D".Example 1import java.util.Scanner; import java.util.regex.Matcher; import java.util.regex.Pattern; public class Example {    public static void main(String args[]) {       //Reading String from user       System.out.println("Enter a String");       Scanner sc = new Scanner(System.in);       String input = sc.nextLine();       String regex = "\D";       //Compiling the regular expression       Pattern pattern = Pattern.compile(regex);       //Retrieving the matcher object       Matcher matcher = pattern.matcher(input);       int count = 0;       ...

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How to match digits using Java Regular Expression (RegEx)

Maruthi Krishna
Maruthi Krishna
Updated on 19-Nov-2019 3K+ Views

You can match digits in a given string using the meta character "\d" or by using the following expression : [0-9]Example 1import java.util.Scanner; import java.util.regex.Matcher; import java.util.regex.Pattern; public class Example {    public static void main(String args[]) {       //Reading String from user       System.out.println("Enter a String");       Scanner sc = new Scanner(System.in);       String input = sc.nextLine();       String regex = "\d";       //Compiling the regular expression       Pattern pattern = Pattern.compile(regex);       //Retrieving the matcher object       Matcher matcher = pattern.matcher(input); ...

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How to match word characters using Java RegEx?

Maruthi Krishna
Maruthi Krishna
Updated on 19-Nov-2019 1K+ Views

The English alphabet (both cases) and, digits (0 to 9) are considered as word characters. You can match them using the meta character “\w”.Example 1import java.util.Scanner; import java.util.regex.Matcher; import java.util.regex.Pattern; public class Example {    public static void main(String args[]) {       //Reading String from user       System.out.println("Enter a String");       Scanner sc = new Scanner(System.in);       String input = sc.nextLine();       String regex = "^\w{5}";       //Compiling the regular expression       Pattern pattern = Pattern.compile(regex);       //Retrieving the matcher object       ...

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