In this little tutorial we’ll walk through the process of getting your dev environment ready for Java.
This will be your Integrated Development Environment (IDE). Anything you can do with IntelliJ you can also do from the command line and a plain ol text editer. The reason we us an IDE is because most of industry uses one. IntelliJ is the most popular one.
If you are running Ubuntu or Mint you can just install it like this:
sudo snap install intellij-idea-community --classic
Otherwise take a look here for full installation instructions: https://www.jetbrains.com/help/idea/installation-guide.html. Please note, we will be using the “community” version.
HelloWorld
)Now let’s make a class file:
HelloWorld
and select Class
public class HelloWorld
{
public static void main(String[] args)
{
String greeting = "Hello World!";
System.out.println(greeting);
}
}
Now let’s run the code: select Run > Run > HelloWorld
You should see something like this appear on the bottom of the screen:
/usr/lib/jvm/java-1.11.0-openjdk-amd64/bin/java -javaagent:/snap/intellij-idea-community/177/lib/idea_rt.jar=32781:/snap/intellij-idea-community/177/bin -Dfile.encoding=UTF-8 -classpath /home/sheena/IdeaProjects/HelloWorld/out/production/HelloWorld HelloWorld
Hello World!
Process finished with exit code 0
That’s it :)
First install openJDK
If you are running Ubuntu Linux or similar then you can just do this:
sudo apt install openjdk-11-jdk
Now let’s take it for a spin.
Make a file called HelloWorld.java
that looks like this:
public class HelloWorld
{
public static void main(String[] args)
{
String greeting = "Hello World!";
System.out.println(greeting);
}
}
Now open up a terminal and cd into the directory containing your new file. Now do this:
ls | grep HelloWorld
javac HelloWorld.java
ls | grep HelloWorld
You should notice a new file called Java.class
. The javac
command compiles the java source code into bytecode.
Now run the following command in your terminal:
java HelloWorld
It should print Hello World!
to the terminal. You just ran the bytecode.
This is another way of interacting with Java. It gets installed automatically when you install the JDK (JDK == Java Development Kit). Type the following at the command line:
jshell
Now you can type in Java statements and they’ll just get executed immediately.
| Welcome to JShell -- Version 11.0.4
| For an introduction type: /help intro
jshell> "Can I get a whoop whoop!".length()
$1 ==> 24
jshell> $1 * 2
$2 ==> 48
jshell> int foo=42
foo ==> 42