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Articles by Maruthi Krishna
Page 4 of 50
Getting the list of all the matches Java regular expressions
Java does not provide any method to retrieve the list of all matches we need to use Lists and add the results to it in the while loop.Exampleimport java.util.ArrayList; import java.util.Iterator; import java.util.Scanner; import java.util.regex.Matcher; import java.util.regex.Pattern; public class ListOfMatches{ public static void main(String[] args) { Scanner sc = new Scanner(System.in); System.out.println("Enter input text: "); String input = sc.nextLine(); String regex = "\d+"; //Creating a pattern object Pattern pattern = Pattern.compile(regex); ArrayList list = new ArrayList(); ...
Read MoreFinding a Match Within Another Match Java regular expressions
To match a pattern within another match you need to compile the regular expression to match the outer pattern find the match retrieve the results and pass the results as input to the inner Matcher object.Exampleimport java.util.Scanner; import java.util.regex.Matcher; import java.util.regex.Pattern; public class MatcherExample { public static void main(String[] args) { int start = 0, len = -1; Scanner sc = new Scanner(System.in); System.out.println("Enter input text: "); String input = sc.nextLine(); String regexOuter = "(.*?)"; String regexInner = "\d+"; ...
Read MoreReplacing all the matched contents Java regular expressions
Once you compile the required regular expression and retrieved the matcher object by passing the input string as a parameter to the matcher() method.You can replace all the matched parts of the input string with another str4ing using the replaceAll() method of the Matcher class.This method accepts a string (replacement string) and replaces all the matches in the input string with it and returns the result.Example 1import java.util.Scanner; import java.util.regex.Matcher; import java.util.regex.Pattern; public class ReplaceAll{ public static void main(String[] args) { Scanner sc = new Scanner(System.in); System.out.println("Enter input text: "); ...
Read MoreNamed captured groups Java regular expressions
Named capturing groups allows you to reference the groups by names. Java started supporting captured groups since SE7.Exampleimport java.util.Scanner; import java.util.regex.Matcher; import java.util.regex.Pattern; public class ReplaceAll{ public static void main(String[] args) { Scanner sc = new Scanner(System.in); System.out.println("Enter input text: "); String input = sc.nextLine(); String regex = "(?[\d]{2})-(?[\d]{5})-(?[\d]{6})"; //Creating a pattern object Pattern pattern = Pattern.compile(regex); //Matching the compiled pattern in the String Matcher matcher = pattern.matcher(input); while (matcher.find()) { ...
Read MoreMatching multiple lines in Java regular expressions
To match/search a input data with multiple lines −Get the input string.Split it into an array of tokens by passing "\r?" as parameter to the split method.Compile the required regular expression using the compile() method of the pattern class.Retrieve the matcher object using the matcher() method.In the for loop find matches in the each element (new line) of the array using the find() method.Reset the input of the matcher to the next element of the array using the reset() method.Exampleimport java.util.regex.Matcher; import java.util.regex.Pattern; public class MatchingText{ public static void main(String[] args) { String input = "sample ...
Read MoreCustom UnaryOperator implementation in java.
The java.util.function.UnaryOperator interface and can be used as assignment target for lambda expressions, it represents operation on a single operand whose result will be of same type as the input. We can create our own UnaryOperator by implementing this interface.The replaceAll() method of the List interface accept an object of the UnaryOperator representing a particular operation performs the specified operation on all the elements of the current list and replaces the existing values with the resultant values.In the following example we are implementing the UnaryOperator interface and creating a custom unary operator object and trying to pass it as an ...
Read MoreRegular expression for a hexadecimal number greater than 10 and should be even in length in java.
Following is the regular expression to match hexadecimal number greater than 10 with even length −^(?=.{10,255}$)(?:0x)?\p{XDigit}{2}(?:\p{XDigit}{2})*$Where,^ − Matches the starting of the sentence.(?=.{10,255}$) − String ending with characters with 10 to 255.\p{XDigit}{2} − Two hexa-decimal characters.(?:\p{XDigit}{2})* − 0 or more sequences of double hexa-decimal characters.$ − Matches the end of the sentence.Example 1import java.util.Scanner; import java.util.regex.Matcher; import java.util.regex.Pattern; public class JavaExample51 { public static void main(String[] args) { Scanner sc = new Scanner(System.in); String nums[] = new String[5]; for(int i=0; i
Read MoreJava regex program to verify whether a String contains at least one alphanumeric character.
Following regular expression matches a string that contains at least one alphanumeric characters −"^.*[a-zA-Z0-9]+.*$";Where, ^.* Matches the string starting with zero or more (any) characters.[a-zA-Z0-9]+ Matches at least one alpha-numeric character..*$ Matches the string ending with zero or more (ant) characters.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(); //Regular expression String regex = "^.*[a-zA-Z0-9]+.*$"; ...
Read MoreJava regex program to add space between a number and word in Java.
You can form matched groups in the regular expression by separating the expressions with parenthesis. In following regular expression the first group matches digits and the second group matches the English alphabet −(\d)([A-Za-z])In short, it matches the part in the input string where a digit followed by an alphabet.Since the expression $1 indicates Group1 and $2 indicates Group2, if you replace The above Java regular expression with $1 $2, using the replace() method (of the String class) a space will be added between number and a word in the given input string when a number is followed by a word.Exampleimport ...
Read MoreRegular Expression E Metacharacter in Java.
The subexpression/metacharacter “\E” ends the quoting begun with \Q. i.e. you can escape metacharacters in the regular expressions by placing them in between \Q and \E. For example, the expression [aeiou] matches the strings with vowel letters in it.Exampleimport java.util.Scanner; import java.util.regex.Matcher; import java.util.regex.Pattern; public class SampleProgram { public static void main( String args[] ) { String regex = "[aeiou]"; Scanner sc = new Scanner(System.in); System.out.println("Enter input string: "); String input = sc.nextLine(); //Creating a Pattern object Pattern pattern = Pattern.compile(regex); ...
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