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Articles by Maruthi Krishna
Page 3 of 50
How to convert a super class variable into a sub class type in Java
Inheritance is a relation between two classes where one class inherits the properties of the other class. This relation can be defined using the extends keyword as −public class A extends B{}The class which inherits the properties is known as sub class or, child class and the class whose properties are inherited is super class or, parent class.In inheritance a copy of super class members is created in the sub class object. Therefore, using the sub class object you can access the members of the both classes.Converting a super class reference variable into a sub class typeYou can try to convert ...
Read MoreCan we override default methods in Java?
An interface in Java is similar to class but, it contains only abstract methods and fields which are final and static.Since Java8 static methods and default methods are introduced in interfaces. Unlike other abstract methods these are the methods can have a default implementation. If you have default method in an interface, it is not mandatory to override (provide body) it in the classes that are already implementing this interface.In short, you can access the default methods of an interface using the objects of the implementing classes.Exampleinterface MyInterface{ public static int num = 100; public default void ...
Read MoreCharacter class: intersection - Java regular expressions
The character classes in Java regular expression is defined using the square brackets "[ ]", this subexpression matches a single character from the specified or, set of possible characters. For example the regular expression [abc] matches a single character a or, b or, c.The intersection variant of the character class allows you to match a character which is common in the ranges that have intersection relation between them.An intersection relation between ranges is defined using && i.e. the expression [a-z&&[r-u]] matches a single character from r to u.Exampleimport java.util.Scanner; import java.util.regex.Matcher; import java.util.regex.Pattern; public class RegexExample1 { public static ...
Read MoreCharacter class: subtraction - Java regular expressions
You can subtract one range from other and use it as new range. You can achieve this by using two variants of character classes i.e. negation and intersection.For example the intersection of ranges [a-l] and [^e-h] gives you the characters a to l as rage subtracting the characters [e-h]Exampleimport java.util.Scanner; import java.util.regex.Matcher; import java.util.regex.Pattern; public class RegexExample1 { public static void main(String[] args) { Scanner sc = new Scanner(System.in); System.out.println("Enter input text: "); String input = sc.nextLine(); String regex = "[a-l&&[^e-h]]"; //Creating a pattern ...
Read MoreRegular Expression Q Metacharacter in Java
The subexpression/metacharacter "\Q" escapes all characters up to "\E" 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.Example import 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); ...
Read MoreJava program to remove all numbers in a string except "1" and "2"?
The regular expression "(?digit(?!\d)" matches the digit specified.The replaceAll() method accepts two strings: a regular expression pattern and, the replacement string and replaces the pattern with the specified string.Therefore, to remove all numbers in a string except 1 and 2, replace the regular expressions 1 and 2 with one and two respectively and replace all the other digits with an empty string.Exampleimport java.util.Scanner; public class RegexExample { public static void main(String args[]) { //Reading String from user System.out.println("Enter a String"); Scanner sc = new Scanner(System.in); String input ...
Read MoreJava regex program to match parenthesis "(" or, ")".
Following regular expression accepts a string with parenthesis −"^.*[\(\)].*$";^ matches the starting of the sentence..* Matches zero or more (any) characters.[\(\)] matching parenthesis.$ indicates the end of the sentence.Example 1import java.util.Scanner; import java.util.regex.Matcher; import java.util.regex.Pattern; public class SampleTest { public static void main( String args[] ) { String regex = "^.*[\(\)].*$"; //Reading input from user Scanner sc = new Scanner(System.in); System.out.println("Enter data: "); String input = sc.nextLine(); //Instantiating the Pattern class Pattern pattern = Pattern.compile(regex); ...
Read MoreCounting the number of groups Java regular expression
You can treat multiple characters as a single unit by capturing them as groups. You just need to place these characters inside a set of parentheses.You can count the number of groups in the current match using the groupCount() method of the Matcher class. This method calculates the number of capturing groups in the current match and returns it.Exampleimport java.util.regex.Matcher; import java.util.regex.Pattern; public class Test { public static void main(String[] args) { String str1 = "This is an example HTML script where ever alternative word is bold."; //Regular expression to match contents of ...
Read MoreRegular 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"); ...
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