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Wednesday, June 2, 2010

Create your first Java program

The following will describe how to create a minimal Java program using Eclipse. It will be the classical "Hello World" program. Our program will write "Hello Eclipse!" to the console.

3.1. Create project

Select from the menu File -> New-> Java project. Maintain "de.vogella.eclipse.ide.first" as the project name. Select "Create separate source and output folders".

Press finish to create the project. A new project is created and displayed as a folder. Open the folder "de.vogella.eclipse.ide.first"

3.2. Create package

Create now a package. A good convention is to use the same name for the top package as the project. Create therefore the package "de.vogella.eclipse.ide.first".

Select the folder src, right mouse click on it and select New -> Package.

3.3. Create Java class

Right click on your package and select New -> Class

Create MyFirstClass, select the flag "public static void main (String[] args)"

Maintain the following code.

package de.vogella.eclipse.ide.first;

public class MyFirstClass {

public static void main(String[] args) {
System.out.println("Hello Eclipse!");


3.4. Run your project in Eclipse

Now run your code. Right click on your Java class and select Run-as-> Java application

Finished! You should see the output in the console.

3.5. Run your Java program outside Eclipse (create jar file)

To run your Java program outside of Eclipse you need to export it as a jar file. Select your project, right click on it and select "Export".

Select JAR file, select next. Select your project and maintain the export destination and a name for the jar file. I named it "myprogram.jar".

Press finish. This will create a jar file in your select output directory.

3.6. Run your program outside Eclipse

Open a command shell, e.g. under Microsoft Windows select Start -> Run and type in cmd. This should open a consle.

Switch to your output directory, e.g. by typing cd path, e.g. if you jar is located in "c:\temp" type "cd c:\temp".

To run this program you need to include the jar file into your classpath. See Classpath and Java JAR Files for details.

java -classpath myprogram.jar de.vogella.eclipse.ide.first.MyFirstClass

Congratulations! You created your first Java project, a package a tiny Java program and you ran this program inside Eclipse and outside


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