Found 9326 Articles for Object Oriented Programming

A string is Palindrome if position of each character remain same in case even string is reversed.For example 'MADAM' is a palidrome string as position of each character remain same even if string 'MADAM' is reversed.Now in order to identify a string as palindrome or not we can use library method approach and also without library method approach.But if we want to check if "Madam" is palindrome or not , it will show us that it is not a palindrome because of the upper case of first letter.Example - Without library method. Live Demopublic class Palindrome {    public static void ... Read More

To count occurence of vowels in a string again use Map utility of java as used in calculating occurence of each character in string.Put each vowel as key in Map and put initial value as 1 for each key.Now compare each character with key of map if a character matches with a key then increase its corresponding value by 1.Examplepublic class OccurenceVowel {    public static void main(String[] args) {       String str = "AEAIOG";       LinkedHashMap hMap = new LinkedHashMap();       hMap.put('A', 0);       hMap.put('E', 0);       hMap.put('I', 0);       hMap.put('O', 0);       hMap.put('U', 0);       for (int i = 0; i

The java.util.LinkedList.listIterator(int index) method returns a list-iterator of the elements in this list (in proper sequence), starting at the specified position in the list.DeclarationFollowing is the declaration for java.util.LinkedList.listIterator() methodpublic ListIterator listIterator(int index)Parametersindex − index of the first element to be returned from the list-iteratorReturn ValueThis method returns a ListIterator of the elements in this list (in proper sequence), starting at the specified position in the listExceptionIndexOutOfBoundsException − if the index is out of rangeExampleThe following example shows the usage of java.util.LinkedList.listIterator() method.Example Live Demopackage com.tutorialspoint; import java.util.*; public class LinkedListDemo {    public static void main(String[] args) { ... Read More

Optional is a container object used to contain not-null objects. Optional object is used to represent null with absent value. This class has various utility methods to facilitate code to handle values as 'available' or 'not available' instead of checking null values. It is introduced in Java 8 and is similar to what Optional is in Guava.Class DeclarationFollowing is the declaration for java.util.Optional class −public final class Optional extends ObjectClass MethodSr.No.Method & Description1static Optional empty()Returns an empty Optional instance.2boolean equals(Object obj)Indicates whether some other object is "equal to" this Optional.3Optional filter(PredicateRead More

instanceof operator is used to check the type of object passed. Following rules explain the usage of instanceof operator in Java.instanceof operator returns true for the object if checked against its class type.instanceof operator returns false for the object if checked against its type which is not in its hierarchy.instanceof operator returns true for the child object if checked against parent object type.instanceof operator returns true for the complete object hierarchy up to the Object class.instanceof operator returns false for the null value.instanceof operator returns false for the parent object if checked against child object type.Following example showcases the above ... Read More

In Java, we use inheritance to allow the creation of a hierarchical classification of classes and objects. As the name suggests, inheritance is the ability of a class to inherit members of another class. The class whose properties are inherited is called a superclass whereas the class that inherits a superclass is called a subclass. We use the extends keyword to inherit the class. There are several types of inheritance in Java such as single and multilevel. In this article, we will specifically explore the multiple inheritance. Multiple Inheritance in Java In the terminology of object-oriented programming, multiple inheritance is ... Read More

Jagged array is a multidimensional array where member arrays are of different size. For example, we can create a 2D array where first array is of 3 elements, and is of 4 elements. Following is the example demonstrating the concept of jagged array.Example Live Demopublic class Tester {    public static void main(String[] args){       int[][] twoDimenArray = new int[2][];       //first row has 3 columns       twoDimenArray[0] = new int[3];       //second row has 4 columns       twoDimenArray[1] = new int[4];       int counter = ... Read More

Collections can be iterated easily using two approaches.Using for-Each loop − Use a foreach loop and access the array using object.Using Iterator − Use a foreach loop and access the array using object.DifferencesConcurrentModificationException − Using for-Each loop, if an object is modified, then ConcurrentModificationException can occur. Using iterator, this problem is elliminated.Size Check − Using for-Each, size check is not required. Using iterator if hasNext() is not used properly, NoSuchElementException can occur.Performance − Performance is similar for both cases.Following is an example of using above ways.Example Live Demoimport java.util.ArrayList; import java.util.Iterator; import java.util.List; public class Tester {    public ... Read More

Often, you will want to cycle through the elements in a collection. For example, you might want to display each element. The easiest way to do this is to employ an iterator, which is an object that implements either the Iterator or the ListIterator interface.Iterator enables you to cycle through a collection, obtaining or removing elements. ListIterator extends Iterator to allow bidirectional traversal of a list, and the modification of elements.Before you can access a collection through an iterator, you must obtain one. Each of the collection classes provides an iterator( ) method that returns an iterator to the start ... Read More

isInstance method is equivalent to instanceof operator. The method is used in case of objects are created at runtime using reflection. General practice says if type is to be checked at runtime then use isInstance method otherwise instanceof operator can be used. See the example below −Example Live Demopublic class Tester{    public static void main(String[] args) throws ClassNotFoundException {       Integer i = new Integer(10);       System.out.println(usingInstanceOf(i));       System.out.println(usingIsInstance(i));    }    public static String usingInstanceOf(Object i){       if(i instanceof String){          return "String";       } ... Read More