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Java Articles
Page 26 of 450
Regular expression "[X?+] " Metacharacter Java
The Possessive Quantifier [X?+] matches the X present once or not present at all.Examplepackage com.tutorialspoint; import java.util.regex.Matcher; import java.util.regex.Pattern; public class PossesiveQuantifierDemo { private static final String REGEX = "T?+"; private static final String INPUT = "abcdTatW"; public static void main(String[] args) { // create a pattern Pattern pattern = Pattern.compile(REGEX); // get a matcher object Matcher matcher = pattern.matcher(INPUT); while(matcher.find()) { //Prints the start index of the match. System.out.println("Match String start(): "+matcher.start()); ...
Read MoreNon capturing groups Java regular expressions:
Using capturing groups you can treat multiple characters as a single unit. You just need to place the characters to be grouped inside a set of parentheses. For example −(.*)(\d+)(.*)If you are trying to match multiple groups the match results of each group is captured. You can get the results a group by passing its respective group number to the group() method. 1, 2, 3 etc.. (from right to left) group 0 indicates the whole match.Exampleimport java.util.Scanner; import java.util.regex.Matcher; import java.util.regex.Pattern; public class CapturingGroups { public static void main( String args[] ) { System.out.println("Enter input text"); ...
Read MoreGetting 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 MorePrint all permutation of a string using ArrayList in Java
In this problem, we are given a string of size n and we have to print all permutations of the string. But this time we have to print this permutation using ArrayList.Let’s take an example to understand the problem -Input − string = ‘XYZ’Output − XYZ, XZY, YXZ, YZX, ZXY, ZYXTo solve this problem, we will be generating all permutations of the character of the string. We will use a recursive function and will return arrayList.ExampleThe following is ArrayList implementation of the algorithm −import java.util.ArrayList; public class Main{ static void printArrayList(ArrayList combo) { combo.remove(""); ...
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 MoreBinaryOperator Interface in Java
The BinaryOperator interface represents an operation upon two operands of the same type, producing a result of the same type as the operands.Following are the methods −Modifier and TypeMethod and DescriptionmaxBy(Comparator
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