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Java Articles
Found 4,495 articles
What is constructor chaining in Java?
Constructors are similar to methods but, They do not have any return type. The name of the constructor is same as the name of the class. Every class has a constructor. If we do not explicitly write a constructor for a class, the Java compiler builds a default constructor for that class. Each time a new object is created, at least one constructor will be invoked. A class can have more than one constructor. this() and super() are used to call constructors explicitly. Where, using this() you can call the current class’s constructor and using super() you can ...
Read MoreHow to instantiate member inner class in Java?\\n
A class that is declared inside a class but outside a method is known as member inner class.We can instantiate a member Inner class in two waysInvoked within the classInvoked outside the classRules for Inner ClassThe outer class (the class containing the inner class) can instantiate as many numbers of inner class objects as it wishes, inside its code.If the inner class is public & the containing class as well, then code in some other unrelated class can as well create an instance of the inner class.No inner class objects are automatically instantiated with an outer class object.If the inner ...
Read MoreHow to find the age when date of birth is known? Using Java?
Java provides a class named Period in the java.time package. This is used to calculate the time period between two given dates as days, months and, years etc.The between() method of this class accepts two LocalDate objects and finds out the period between the two given dates (number of years, months, and days) and returns as a period object.From this, you can extract the number of days, months and, years of the period in between using the getDays(), getMonths() and, getYears() respectively.Finding the ageIf you already have the date of birth of a person, to find the age −Get the ...
Read MoreWhat is ‘this’ reference in Java?
The this is a keyword in Java which is used as a reference to the object of the current class, with in an instance method or a constructor. Using this you can refer the members of a class such as constructors, variables and methods.Using “this” you can −Differentiate the instance variables from local variables if they have same names, within a constructor or a method.class Student { int age; Student(int age) { this.age = age; } }Call one type of constructor (parametrized constructor or default) from other in a class. It is known as ...
Read MoreHow to Get a slice of a primitive array in Java?
You can get a part of a Java array in between two specified indexes in various ways.By Copying contents:One way to do so is to create an empty array and copy the contents of the original array from the start index to the endIndex.Exampleimport java.util.Arrays; public class SlicingAnArray { public static int[] sliceArray(int array[], int startIndex, int endIndex ){ int size = endIndex-startIndex; int part[] = new int[size]; //Copying the contents of the array for(int i=0; iarray[i]); part = stream.toArray(); //Copying the contents of the array for(int i=0; i
Read MoreTypes of quantifiers in Java regex
If you want to specify the number of occurrences while constructing a regular expression you can use quantifiers. Java supports three types of quantifiers namely: greedy quantifiers, reluctant quantifiers and possessive quantifiers.Greedy quantifiers − Greedy quantifiers are the default quantifiers. A greedy quantifier matches as much as possible from the input string (longest match possible) if match not occurred it leaves the last character and matches again.Exampleimport java.util.Scanner; import java.util.regex.Matcher; import java.util.regex.Pattern; public class Test { public static void main(String[] args) { Scanner sc = new Scanner(System.in); System.out.println("Enter input text: "); ...
Read MoreJava program to sort words of sentence in ascending order
To sort words of sentence in ascending order, the Java code is as follows −Exampleimport java.util.*; public class Demo{ static void sort_elements(String []my_str, int n){ for (int i=1 ;i= 0 && temp.length() < my_str[j].length()){ my_str[j+1] = my_str[j]; j--; } my_str[j+1] = temp; } } public static void main(String args[]){ String []my_arr = {"This", "is", "a", "sample"}; int len = my_arr.length; sort_elements(my_arr,len); System.out.print("The sorted array is : "); for (int i=0; i
Read MoreWhy do we need generics in Java?
Reference typesAs we know a class is a blue print in which we define the required behaviors and properties and, an interface is similar to class but it is a Specification (containing abstract methods).These are also considered as datatypes in Java, unlike other primitive datatypes a literal of these kind of types points/refers to the location of the object. They are also known as reference types.GenericsGenerics is a concept in Java where you can enable a class, interface and, method, accept all (reference) types as parameters. In other words it is the concept which enables the users to choose the ...
Read MoreDifference Between Daemon Threads and User Threads In Java
As we know java is a language that supports multi threading and on the basis of nature threads in java are classified into two types Daemon thread and User thread.The following are the important differences between Daemon Threads and User Threads.Sr. No.KeyDaemon ThreadsUser Threads1NatureDaemon thread is low in priority i.e JVM does not care much about these types of threads.User threads are recognized as high priority thread i.e. JVM will wait for any active user thread to get completed.2CPU availabilityIt is not guaranteed that Daemon thread always gets CPU usage whenever it requires due to its low priority.User thread always ...
Read MoreMatching Nonprintable Characters using Java regex
There are 7 common non printable characters used in general and each character has its own hexadecimal representation.NamecharactersHexa-decimal representationbell\a0x07Escape\e0x1BForm feed\f0x0CLine feed0x0ACarriage return\r0X0DHorizontal tab\t0X09Vertical tab\v0X0BExample 1import 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 = "\x09"; //Creating a pattern object Pattern pattern = Pattern.compile(regex); //Matching the compiled pattern in the String Matcher matcher = ...
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