Java with BlueJ

Assuming you have excellent knowledge of POP, in this blog, we will cover OOP and Java language with significant coding on BLUEJ.

What is BlueJ?

 

BlueJ is an integrated development environment for the Java programming language, developed mainly for educational purposes, but also suitable for small-scale software development. It runs with the help of JDK.

BlueJ was developed to support the learning and teaching of object-oriented programming, and As a result, its design differs from other development environments.

History: 

The development of BlueJ was started in 1999 by Michael Kölling and Joh Rosenberg at Monash University, as a successor to the Blue system.

The latest version of BlueJ:

Version 4.2.2 was released on 4th October 2019.

 

Issues in the previous version:

Fixed an issue with an extra space appearing in the terminal before the first output.

It was fixed not being able to alter the preferences for the Submitter extension.

To download this amazing BlueJ Software use below link:

             https://bluej.org/

 

Installation Procedure

 

·       Download the installer, making sure to keep track of where it is in the file system.

·       Start your Command Prompt or Terminal application like Windows Power Shell. You will complete the installation by typing some commands into this application. (For Windows users, see these instructions for "how to start the Command Prompt").

·       Run the following command:

 

>>>Java -jar<path-to-bluej-installer>

... Replace <path-to-bluej-installer> with the correct path to the installer,  .jar file that you have downloaded.

·       If you receive a "command not found" or similar error, you may need to specify the full path to the Java executable. For example

 

>>>"C:\Program Files\Java\jdk1.8.0_144\bin\java.exe" -jar >>>"C:\Users\Sarah\Downloads\bluej-411.jar"

(This is an example is for Windows users; other operating system paths usually use a slash( ’/’ ) symbol as a path separator!).

· The installer should start and present a window where you can specify both the path to the JDK and for BlueJ 4.2.0 the way to OpenJFX, (make sure it is correct!) and where you want to install BlueJ. It is usually best to install BlueJ somewhere under your home folder. Take note of the path as you will need it to run BlueJ later.

Running BlueJ

To run BlueJ:

 

• On Windows:

·        Start the Command Prompt application.

·        Change into the directory where you installed BlueJ:

>>>cd <path-to-bluej-installation>

 

... replacing <path-to-bluej-installation> with the path you chose to install BlueJ to.

·        Start the BlueJ batch file:

>>> bluej.bat

• On other operating systems:

·        Start the Terminal application.

·        Change into the directory where you installed BlueJ:

>>> cd <path-to-bluej-installation>

... replacing <path-to-bluej-installation> with the path you chose to install BlueJ to.

·        Start the BlueJ shell script file:

>>>./bluej

 

Steps for the running program on BlueJ

·        At first, double click on the BlueJ icon, which is present on the desktop.

·        Click on the Project option on the menu bar of BlueJ windows. It enables you to create a directory.

·        Click on Project and select New Project from the drop-down menu.

·        Enter the file name in space provided (say, Com Appl 10) and click Create.

·        A window appears with the project icon.

·        Click on the New Class button.

·        Write the Class name (say, Welcome) and click OK.

·        Now, double click on the folder named Welcome to open the class. A sample structure of the class appears on the screen.

·        Select and delete the sample structure.

·        Now, start writing your program as illustrated below. Compile your program, which displays the message: 'Class compiled -no syntax errors' otherwise, debug and recompile the program unless it is error-free.

 

Line and word description.

 

  Line 1: It is a comment line.

  Line 2: Declaration of a class, i.e. (public class Welcome)

  Line 3: Opening of the class with {

  Line 4: It contains the main function. The execution of the file commences from the main () function.

  Public: It declares that the file access has no restriction

  Static: It is a keyword. It instructs the compiler, so that main () should run before anything else in the program.

  Void: It indicates that main () will not return anything

  String args []: It declares a string array, "args" stands for arguments.

  Line 5: It indicates the starting of the main function by an opening brace {

  Line 6: These are only executable statements of the program.

  Line 7: closing brace}, to close the main function

  Line 8: closing brace}, to close the class.

 

Execution of the Program

 

The following steps are to be done to execute a java program.

·       Select the icon of the class (say, class name) and click the right button of the mouse.

·       A drop-down menu appears on the screen. Select and click void main (String [] args).

·       A method call window appears on the screen. Click OK.

·       The desired output of the program appears as shown below

 

Differences between JDK 1.3 and BlueJ

 

Some sprinkle of OOP and JAVA

 

Define: An Object-Oriented Programming (OOP) is a modular approach, which allows the data to be applied within the stipulated program area. It also provides the reusability feature to develop productive logic, which means to give more emphasis on data.

 

Define: Object is a unique entity, which contains data and functions (characteristics and behavior) together in an Object-Oriented Programming (OOP) Language.

 

Define: A class is simply a representation of the type of objects. It is the blueprint/ plan/ template that describes the details of an object. A class is a blueprint from which the individual objects are created. Class is composed of three things viz. a name, attributes and operations.

 

Define: Wrapping of data and functions of a class together so that they can be applied as a unit to perform any operation is termed as Encapsulation.

 

Define: Abstraction refers to an act of representing essential features without including background details.

 

Define: Inheritance is the process in which objects of one class can link and share some common properties of the objects with another class.

 

Define: Polymorphism is the process of using a function for more than one purpose. It allows the use of the different internal structures of the object by keeping the same external interface.

 

Define: Dynamic binding is the process that links the function call with function signature at runtime, i.e., during the execution of a program.

 

Benefits of the Object-Oriented Programming (OOP)

 

There are many benefits of OOP to the programmers as well as the users. Some benefits of OOP are listed below:

 

·       You can extend the use of an existing class through inheritance.

·       Using the concept "data hiding," you can generate a secured program.

·       Multiple instances of an object can be created to co-exist without any interference.

·       You can create different modules in your project through objects.

·       It is highly beneficial for solving complex problems.

·       It is easy to modify and maintains software complexity.

 

By: Aaditya Rasala

Currently pursuing B.E. in Computer Engineering as professional life. with a bit of interest in photography, adventure, and learning new stuff.

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