Eclipse (@ www.eclipse.org) is an open-source Integrated Development Environment (IDE) supported by IBM. Eclipse is popular for Java application development (Java SE and Java EE) and Android apps. It also supports C/C++, PHP, Python, Perl, and other web project developments via extensible plug-ins. Eclipse is cross-platform and runs under Windows, Linux and macOS.
Writing your First Java Program in Eclipse
Step 0: Launch Eclipse
- Launch Eclipse by running “
eclipse.exe” from the Eclipse installed directory. - Choose an appropriate directory for your workspace, i.e., where you would like to save your files (e.g.,
c:\myProject\eclipsefor Windows) ⇒ Launch. - If the “Welcome” screen shows up, close it by clicking the “close” button next to the “Welcome” title.
Step 1: Create a new Java Project
For each Java application, you need to create a project to keep all the source files, classes and relevant resources.
To create a new Java project:
- Choose “File” menu ⇒ “New” ⇒ “Java project” (or “File” ⇒ “New” ⇒ “Project” ⇒ “Java project”).
- The “New Java Project” dialog pops up.
- In “Project name”, enter “
FirstProject“. - Check “Use default location”.
- In “JRE”, select “Use default JRE (currently ‘JDK11.0.x’)”. But make sure that your JDK is 1.8 and above.
- In “Project Layout”, check “Use project folder as root for sources and class files”.Push “Finish” button.
- In “Project name”, enter “
- In “Create module-info.java” dialog, Click “Don’t Create”. (Note: For easier version of Eclipse, you need to use the “Next” Button in the previous step, and uncheck “Create module-info.java file”).
Step 2: Write a Hello-world Java Program
- In the “Package Explorer” (left pane) ⇒ Right-click on “
FirstProject” (or use the “File” menu) ⇒ New ⇒ Class. - The “New Java Class” dialog pops up.
- In “Source folder”, keep the “FirstProject”.
- In “Package”, delete the content if it is not empty.
- In “Name”, enter “
Hello“. - Check “
public static void main(String[] args)“. - Don’t change the rest.Push “Finish” button.
- The source file “
Hello.java” opens on the editor panel (the center pane). Enter the following codes:public class Hello { public static void main(String[] args) { System.out.println(“Hello, world!”); } }
Step 3: Compile & Execute the Java Program
- There is no need to compile the Java source file in Eclipse explicitly. It is because Eclipse performs the so-called incremental compilation, i.e., the Java statement is compiled as and when it is entered.
- To run the program, right-click anywhere on the source file “
Hello.java” (or choose “Run” menu) ⇒ Run As ⇒ Java Application. - The output “Hello, world!” appears on the Console panel (the bottom pane).
NOTES:
- You should create a NEW Java project for EACH of your Java application.
- Nonetheless, Eclipse allows you to keep more than one programs in a project, which is handy for writing toy programs (such as your tutorial exercises). To run a particular program, open and right-click on the source file ⇒ Run As ⇒ Java Application.
- Clicking the “Run” button (with a “Play” icon) runs the recently-run program (based on the previous configuration). Try clicking on the “down-arrow” besides the “Run” button.
- references:www3.ntu.edu.sg