by Dinesh Thakur

There are times when you want to prevent inheritance. Perhaps there is no need the extensibility for various reasons. If you know this for sure, there are advantages to declaring the final keyword precisely that.

Java has a special keyword called final that can use for creating final methods, final classes, and final variables. The final modifier is void, which simply means that no value is returned.The final modifier indicates that the value of this member cannot change. We get a compile-time error if our program tries to change its contents. Each of these is explained in more detail next.

 
by Dinesh Thakur

Java is a robust, general-purpose, high-level programming language and a powerful software platform. It is also object-oriented, distributed, portable and multi-threaded. Java follows the 'Write - once - run - anywhere' approach. All Java programs must run on the Java platform that has two components, the Java Virtual Machine (JVM) and the Java Application Programming Interface (API).

 
by Dinesh Thakur

Keywords also are known as reserved words are the pre-defined identifiers reserved by Java for a specific purpose that inform the compiler about what the program should do. A Keyword is that which have a special meaning those already explained to the java language like int, float, class, public, etc. these are the reserved keywords. These special words cannot be used as class names, variables, or method names, because they have special meaning within the language.



 
by Dinesh Thakur

In computer science, “type casting” and “type conversion” refers when there is either implicitly or explicitly is a conversion from one data type to another. When both types of expression are compatible with each other, then Data type conversions from one type to another can be carried out Automatically by java compiler. However, there is a technical difference between type conversion and type casting, i.e. type conversion is carried out “automatically” by java compiler while the "type casting" (using a cast operator) is to be explicitly performed by the java programmer.It is usually classified into two categories



 
by Dinesh Thakur

Type Casting: The process of converting one data type to another is called casting. Casting is often necessary when a function returns a data of type in different form then we need to perform an operation. Under certain circumstances Type conversion can be carried out automatically, in other cases it must be "forced" manually (explicitly). For example, the read() member function of the standard input stream (System.in) returns an int. If we want to store data of type int returned by read() into a variable of char type, we need to cast it :



 
by Dinesh Thakur

Java Tokens:- A java Program is made up of Classes and Methods and in the Methods are the Container of the various Statements And a Statement is made up of Variables, Constants, operators etc . 



 
by Dinesh Thakur

Java Literals: A literal in java refers to a fixed value that appears directly in a program. Java define five primary types of literals. By literal we mean any number, text, or other information that represents a value. This means what you type is what you get. They are commonly known as constants. We will use literals in addition to variables in Java statement.



 
by Dinesh Thakur

Identifiers in Java. A Java identifier is the symbolic name that is used for identification purpose. In Java, an identifier can be a variable name, constant name, method name, class name, array name, packages name or an interface. Few authors term variables as an identifier. For example : int score = 100;

 
by Dinesh Thakur

When you create an object by instantiating a class, the object uses some memory. After an object in memory has been used and is no longer needed, it is sensible to free memory from that object. Unlike some object-oriented languages where you have to explicitly destroy the objects that are no more references to that object. References that held in a variable naturally dropped when the variable goes out of scope. Alternatively, we can explicitly drop an object reference by setting the variable to null. which is a tedious and error-prone task, Java follows a different approach.

 
by Dinesh Thakur

In Java 1.5, a new class known as Scanner class was introduced to simplify the task of getting input from the user. The Scanner class is in java.util package which allows the user to read the data dynamically from the keyboard. It can be used to read a File on the disk. The Java Scanner class extends Object class is present in java.lang package and implements Iterator and Closeable interfaces.



 
by Dinesh Thakur

The this keyword in Java is used when a method has to refer to an object that has invoked it. It can be used inside any method to refer to the current object. This means that this is always used as a reference to the object on which the method was invoked. We can use this anywhere as reference to an object of the current class type is permitted.

 
by Dinesh Thakur

Objects and classes are the essential concepts in OOP as they are what we use for writing our programs. Java objects may be both physical and logical entities, but classes are only logical entities.

In the real world, you'll often find many individual objects all of the same kind.All the objects that have similar properties and similar behavior are grouped together to form a class.

 
by Dinesh Thakur

The different languages reflect the different styles of programming. OOP or object-oriented programming is a style of programming with a firm basis in several concepts. Those concepts revolve around objects and classes and include Polymorphism, Encapsulation, Inheritance, Abstraction and more.  Java is one of the most popular of all the object-oriented programming languages, as well as one of the easiest to learn and use.   
Any application built on objects in Java is an object-oriented application and is based on the declaration of one or more classes, with an object created from those classes and the interaction between the objects.    

 
by Dinesh Thakur

Initializing a variable is considered very helpful while making programs. We can initialize variables of primitive types at the time of their declarations. For example:

int a =10;

In Object Oriented Programming language (OOPL) like Java, the need of initialization of fields of a new object is even more common. We have already done this using two approaches.

 
by Dinesh Thakur

Polymorphism is a very powerful concept that allows you to design amazingly flexible applications. The word 'Polymorphism: is derived form two Greek words 'poly' which means many and 'morphos' which means forms. So, polymorphism means the ability to take many forms.

 
by Dinesh Thakur

Defination : The objects, are the building blocks of the object oriented programming language. In some situations, a programer may use multiple objects belonging to different classes which may have some kind of relationship among themselves as they share some common features.

Let us consider an example of a program containing objects of two different classes Car and Motorcycle for maintaining car and motor cycle information respectively. Both Car and Motorcycle classes exhibit some kind of relationship as both are a kind of vehicle and share some common features like speed, engine specification etc. To represent relationship between classes, we use the concept of Inheritance.



 
by Dinesh Thakur

Definition: Encapsulation and data hiding are the key features of object oriented programming. Encapsulation refers to the ability to package related behavior in an object bundle and control or restrict their access in both function and data from other objects. It necessarily is all about packaging related stuff together and keeping them away from external elements. You will note that keywords encapsulation along with data hiding is used interchangeably all over.

 
by Dinesh Thakur

Java interface used for achieving 100% abstraction because of the interface only contains methods without any implementation or body. However, it contains only abstract methods and constants (final fields). Any field that declared inside interface is public, static, and final by default, any method is an abstract public method. It specifies what must be done but not how. Once an interface is defined, class implements an interface by providing an implementation for each method declared by the interface. Also one class can implement any number of interfaces. Interfaces have the following advantages.

 
by Dinesh Thakur

Immutable class means unmodifiable or unchangeable, i.e., once the object has been created, they are immutable objects, there is no way to modify the text it represents. In Java, all primitive java.lang package wrapper classes (like String, Boolean, Byte, Short, Integer, Long, Float, Double, etc.) and String classes are immutable.



 
by Dinesh Thakur

All the Previous Languages are Structured or we can say that they were procedural programming means in them processing is to be done in sequence manner and These are also called the Top down or either they were bottom up Languages Most Important things those must be in the Languages are Reliability, Maintainability and Reusability and user Friendly So For Achieving these things they Developed java.



 

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About Dinesh Thakur

Dinesh ThakurDinesh Thakur holds an B.SC (Computer Science), MCSE, MCDBA, CCNA, CCNP, A+, SCJP certifications. Dinesh authors the hugely popular blog. Where he writes how-to guides around Computer fundamental , computer software, Computer programming, and web apps. For any type of query or something that you think is missing, please feel free to Contact us.