26 September 2016

Write a program in Java to show all files and directory name of a given location




Solution: 
If you want to run this Java program, you have to do the following:
  • Step1: Your computer must have JDK installed to run and compile any Java program.
  • Step2: Create a file name DirfileList.java with the source code given bellow and save the file on any location on your computer.
  • Step3: Compile and  Run the java program to get the output.

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import java.io.File;
import java.util.ArrayList;
import java.util.List;

public class DirfileList {

    public static void main(String[] args) {
        // TODO code application logic here

        try {
            // Set directory path name 
            File path = new File("F:/test");

            // Get list of files
            File[] listOfFiles = path.listFiles();

            // Declare file name list
            List<String> file_names = new ArrayList<String>();

            // Declare directory name list
            List<String> dir_names = new ArrayList<String>();

            // Loop throw the files and directory name and store the names in List
            for (int i = 0; i < listOfFiles.length; i++) {

                if (listOfFiles[i].isFile()) {
                    file_names.add(listOfFiles[i].getName());
                } else if (listOfFiles[i].isDirectory()) {
                    dir_names.add(listOfFiles[i].getName());
                }
            }

            // Print file names
            for (String fName : file_names) {
                System.out.println("File:" + fName);
            }

            // Print directory names
            for (String dName : dir_names) {
                System.out.println("Directory:" + dName);

            }
        } catch (Exception e) {
            System.out.println("!! Error:" + e.toString());
        }

    }

}

Java: A Beginner's Guide, Sixth Edition

01 June 2016

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.

Core JavaServer Faces (3rd Edition)
Mastering JavaServer Faces (Java)

29 May 2016

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.

Programming Languages
Error Types, Systematic Debugging, Exceptions

21 April 2016

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.
Inheritance



  1. Single inheritance : Where subclasses inherit the features of one super class. A class acquires the properties of another class.  
    Single Inheritance
  2. Multiple inheritance: Where one class can have more than one super class and inherit features from all parent classes. 
    Multiple Inheritance
  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. 
    Multilevel Inheritance
  4. Hybrid inheritance: a mix of two or more of the above types of inheritance.

Object-Oriented Programming in C++ (4th Edition)
Object-Oriented Programming for Dummies

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

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

PolymorphismSams Teach Yourself C++ in One Hour a Day (7th Edition)

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. 
Encapsulation


  • 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.

Intro to Java Programming, Comprehensive Version (10th Edition)
Java: How to Program, 9th Edition (Deitel)

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. 
    Object-Oriented Programming (oop)
  • 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. 
    Objects of Object-Oriented Programming
  • 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.
PHP Advanced and Object-Oriented Programming: Visual QuickPro Guide (3rd Edition) (Visual QuickPro Guides)

What is Java Bytecode ?


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.


Java: A Beginner's Guide, Seventh Edition

What is Java Applets and Java Servlet ?


Java Applet
  • An Java applet is a special kind of small Java program that is designed to be transmitted over the Internet and automatically executed by a Java-compatible web browser. 
  • Applet are typically used to display data provided by the server, handle user input, or provide simple functions, such as a loan calculator, that execute locally on client machine, rather than on the server.
  • An applet is downloaded on demand, without further interaction with the user. 
  • When a user clicks a link that contains an applet, the applet will be automatically downloaded and run in the browser.
    Java Applets and Java Servlet
 Java Servlet:
  • A servlet is a small program that executes on a server. 
  • Servlets dynamically extend the functionality of a web server and applets dynamically extend the functionality of a web browser. 
  • Java spanned both sides of the client/server connection with Applet and Servlet.



Java: The Complete Reference, Tenth Edition (Complete Reference Series)

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