What is JavaServer Faces (JSF) in Java programming language ?

• JSF is a component-based MVC(Model View Controller) framework which enables you to completely separate Java code from HTML pages. 
• It is a new technology for developing server-side Web applications using Java.

• For example: to display a table with rows and columns you can add a table component to a page, there is no need to write html table , tr ,td tags with loop structure to show table data in JSF.

• JSF has the following parts:

• A set of user interface components(HTML tags, form, table, JSF component)
• An event-driven programming model
• A component model that enables third-party developers to supply additional components

• The application developed using JSF is easy to debug and maintain.

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What do you mean by Exception handling in programming language?

• An exception is an error that occurs at run time. 
• Run time errors are errors that cause a program to terminate abnormally. 
• Run time errors occur while a program is running if the environment detects an operation that is impossible to carry out.
• Most of the well known computer programming language like Java, C++ have exception handling  mechanism by which a programmer can handle run-time errors of the program. 
• Some common exceptions are divide-by-zero or file-not-found etc.

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What is Inheritance in OOP(Object Oriented Programming) ?

• Inheritance is the process by which one object can acquire the properties of another object.

• In reality as Children get properties from Parents. Similarly in OOP(Object Oriented Programming) using inheritance a Child class can extends the data and member from its parent class.

• There are various types of inheritance, based on paradigm and specific language.

1. Single inheritance : Where subclasses inherit the features of one super class. A class acquires the properties of another class.  
   
2. Multiple inheritance: Where one class can have more than one super class and inherit features from all parent classes. 
   
3. Multilevel inheritance : Where a subclass is inherited from another subclass. Hierarchical inheritance: Where one class serves as a superclass (base class) for more than one sub class. 
   
4. Hybrid inheritance: a mix of two or more of the above types of inheritance.

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What is Polymorphism in OOP ?

• Polymorphism (from Greek, meaning “many forms”) is the mechanism that allows one interface/method/function/procedure to access a general class of actions.  
• More generally, the concept of polymorphism is often expressed by the phrase “one interface,  multiple methods.” 
• This means that it is possible to design a generic interface to a group of related activities.

• Polymorphism helps reduce complexity by allowing the same interface to be used to specify a general class of action.

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What do you mean by encapsulation in OOP ?

• Encapsulation is a programming mechanism that binds together code and the data it manipulates and apply restricting access to some of the object's components. 

• In an object-oriented language, it is a language construct that facilitates the bundling of data with the methods or other functions operating on that data. 

• Class (extensible program-code-template for creating objects) is used to ensure encapsulation of data and method in Object Oriented Programming.

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What do you mean by Object-Oriented Programming ?

• Object-oriented programming (OOP) is a programming paradigm based on the concept of objects which may contain data and code what will operate on the data. 
• Object refers to a particular instance of a class where the object can be a combination of variables, functions, and data structures. 
  
• In OOP the variable declared inside a Class (self defined data type like int, char, float etc is primitive type ) is called Data & the function declared inside a Class is called method. 
• Object-oriented programming took the best ideas of structured programming and combined them with several new concepts. It is a different way of organizing a program. 
  
• Example: In reality everything is object of its class like CAR is an object of CAR class. Any person is an object of Human Class, Mango is an object of Fruit class, Rose is an object of Flower class etc.

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What is Java Bytecode ?

• When a Java program source is compiled, the output of the Java compiler is called bytecode. 
• Many language generate executable code after compilation. 
• In Java the output is converted to a special type of file which is called the bytecode.
• Bytecode is a highly optimized set of instructions designed to be executed by the Java run-time system,which is called the Java Virtual Machine (JVM). 
• Bytecode makes it much easier to run a program in  a wide variety of environments because only the JVM needs to be implemented for each  platform.

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