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Object Oriented Programming Articles
Page 213 of 589
Can we assign values to final arrays in Java?
The array is a container that can hold a fixed number of items and these items should be of the same type. Most of the data structures make use of arrays to implement their algorithms. The following are the important terms to understand the concept of Array.Element − Each item stored in an array is called an element.Index − Each location of an element in an array has a numerical index, which is used to identify the element.The size of the array will be determined at the time of creation.Examplepublic class ArrayExample { public static void main(String args[]){ ...
Read MoreTraversing contents of a hash map in Java
A map is a collection in Java which stores key-value pairs. The keys of this must not be null and each key should point to only one value. It is represented by the Map interface of java.util package. There are various classes which provide implementation to this interface.The HashMap is a class which implements the Map interface. It is based on the Hash table. It allows null values and null keys.In short, you can store key-value pairs in the HashMap object. Once you do so you can retrieve the values of the respective keys but, the values we use for ...
Read MoreAssigning arrays in Java.
While creating variables first of all we will declare them, initialize them, assign/re-assign values to them.Similarly, while creating arrays −You can declare an array just like a variable −int myArray[];You can create an array just like an object using the new keyword −myArray = new int[5];You can initialize the array by assigning values to all the elements one by one using the index −myArray [0] = 101; myArray [1] = 102;Assigning values to an arrayWhen we assign primitive values of one type to a variable of other (datatype) implicitly they are converted.But, when you try to assign a higher datatype ...
Read MoreAre Generics applied at compile time or run time?
Generics 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 reference type that a method, constructor of a class accepts, dynamically. By defining a class as generic you are making it type-safe i.e. it can act up on any datatype.Exampleclass Student{ T age; Student(T age){ this.age = age; } public void display() { System.out.println("Value of age: "+this.age); } } public class GenericsExample { ...
Read MoreCan you create an array of Generics type in Java?
Generics 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 reference type that a method, constructor of a class accepts, dynamically. By defining a class as generic you are making it type-safe i.e. it can act up on any datatype.Exampleclass Student{ T age; Student(T age){ this.age = age; } public void display() { System.out.println("Value of age: "+this.age); } } public class GenericsExample { ...
Read MoreHow many ways are there to initialize the instance variables of a class in java?
You can initialize the instance variables of a class using final methods, constructors or, Instance initialization blocks.Final methodsWhenever you make a method final, you cannot override it. i.e. you cannot provide implementation to the superclass’s final method from the subclass.i.e. The purpose of making a method final is to prevent modification of a method from outside (child class). You can also use these final methods to initialize the instance variables.Exampleimport java.util.Scanner; public class FinalMethods { int age = getAge(); String name = getName(); static Scanner sc = new Scanner(System.in); public static final int getAge() { ...
Read MoreWhat is need of introducing Generics, when Arrays already present in Java?
Arrays in Java are used to store homogeneous datatypes, where generics allow users to dynamically choose the type (class) that a method, constructor of a class accepts, dynamically.By defining a class generic you are making it type-safe i.e. it can act up on any datatype. To understand generics let us consider an example −Exampleclass Student{ T age; Student(T age){ this.age = age; } public void display() { System.out.println("Value of age: "+this.age); } } public class GenericsExample { public static void main(String args[]) { Student std1 ...
Read MoreHow to access the fields of an interface in Java?
An interface in Java is a specification of method prototypes. Whenever you need to guide the programmer or, make a contract specifying how the methods and fields of a type should be you can define an interface. By default, All the members (methods and fields) of an interface are public.All the methods in an interface are public and abstract (except static and default).All the fields of an interface are public, static and, final by default.If you declare/define fields without public or, static or, final or, all the three modifiers. Java compiler places them on your behalf.ExampleIn the following Java program, ...
Read MoreIs it possible to instantiate Type-parameter in Java?
Generics 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 reference type that a method, constructor of a class accepts, dynamically. By defining a class as generic you are making it type-safe i.e. it can act up on any datatype.Exampleclass Student { T age; Student(T age){ this.age = age; } public void display() { System.out.println("Value of age: "+this.age); } } public class GenericsExample { ...
Read MoreCan we synchronize abstract methods in Java?
An abstract method is the one that does not have a body. It contains only a method signature with a semi colon and, an abstract keyword before it.public abstract myMethod();To use an abstract method, you need to inherit it by extending its class and provide implementation (body) to it. If a class contains at least one abstract method, you must declare it abstract.Exampleimport java.io.IOException; abstract class MyClass { public abstract void display(); } public class AbstractClassExample extends MyClass{ public void display(){ System.out.println("subclass implementation of the display method"); } public static void main(String args[]) ...
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