Table of Contents

Run Java Code using BlueJ IDE.

To run your code, you must create an instance of the class containing the main method. The main method is the entry point of any Java application, where the program execution begins.

Running a BlueJ project involves a few steps to ensure your code is correctly compiled and executed.

Steps to run code

The general steps to run your Java code using the BlueJ IDE are as follows:

Launch BlueJ IDE. Launch the BlueJ IDE from your computer’s desktop shortcut or the Start Menu.
Create or Open an existing Project.
If you already have a BlueJ project, you can open it by selecting Project from the menu and then Opening the Project. Then, navigate to your project’s folder and select it.
If you don’t have a project, create a new one by selecting Project > New Project.

Create Project Components

A Java project consists of the following components:

Classes are the fundamental building blocks of any Java application. A class defines the attributes (fields) and behaviors (methods) of objects created from the class. Classes encapsulate data and functionality.

Interfaces define a contract that classes can implement. An interface specifies a set of methods a class must implement. In Java, interfaces allow for abstraction and multiple inheritance.

Packages are used to group related classes and interfaces together. Packages help organize the project and avoid naming conflicts. For example, java.util is a package that contains utility classes.

Configuration Files and Resources

Compile Classes

To ensure that all your classes in the project are compiled, click the Compile button in the toolbar or right-click each class and select the Compile menu option.

BlueJ will automatically compile your code when you make changes, but you can also manually compile it to ensure it is up to date.

Create Objects

To run your code, you must create an instance of the class containing the main method.
Right-click on the class using the main method and select Create Object. This creates an instance of that class.

Run Java Code using BlueJ IDE

To run the main method, right-click the created object and select void main(String[] args)

You can also run other methods directly by right-clicking on the created object and selecting the method you want to execute from the list of available methods.

View Output

Any output from your program will appear in the BlueJ terminal window at the bottom of the screen.

Test the Application

To verify the application works as expected, you need to test the application and its behavior. You can write test code in Test classes to test your application.