1.3. Java in the Terminal¶

1.3.1. Mac Users¶

Let’s write a simple “Hello, World” program and watch the JDK in action.

In the future, we’ll be doing most of our Java coding with the IntelliJ IDE. IntelliJ contains many features to help us write Java properly and easily, including its own compiler. For now though, we’ll use a simpler text editor so we can demonstrate what we get with the JDK.

In the text editor of your choice, create and save a file called HelloWorld.java and include the code below:

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public class HelloWorld {

   public static void main(String[] args) {

      System.out.println("Hello, World");
   }

}

We’ll discuss the syntax of this program soon, but you can likely predict that this program has an expected output of “Hello, World”. To test this hypothesis, open a terminal window and navigate to the parent directory of your new file. Run:

java HelloWorld.java

You should see your greeting printed!

Recall from the walk-through on the previous page, Java needs to be compiled before executing. Java version 11 introduced the capability to compile single-file Java programs without explicitly running a command to compile. If our Hello, World program were more complex and contained another file, we would need to first run javac HelloWorld.java, to compile, followed by java HelloWorld.java.

1.3.2. Windows Users¶

Let’s write a simple “Hello, World” program and watch the JDK in action.

In the future, we’ll be doing most of our Java coding with the IntelliJ IDE. IntelliJ contains many features to help us write Java properly and easily, including its own compiler. For now though, we’ll use a simpler text editor so we can demonstrate what we get with the JDK.

In the text editor of your choice, create and save a file called HelloWorld.java and include the code below:

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public class HelloWorld {

   public static void main(String[] args) {

      System.out.println("Hello, World");
   }

}

We’ll discuss the syntax of this program soon, but you can likely trust your gut that this program has an expected output of “Hello, World”.

To test this hypothesis, open a terminal window and navigate to the parent directory of your new file. In a separate window, navigate to the bin folder in the Java Development Kit to get the file path (the image below shows you how to get there from the C: Drive). Copy the file path.

Run the following command, replacing the {filepath} with the file path to your JDK that you just copied:

set PATH=%PATH%;{filepath}

This command sets a path in our system for java so that we can compile and run Java programs. To make use of the new java command, you may have to restart your terminal window by closing it and opening a new one.

java HelloWorld.java

You should see your greeting printed!

Recall from the walk-through on the previous page, Java needs to be be compiled before executing. Java version 11 introduced the capability to compile single-file Java programs without explicitly running a command to compile. If our Hello, World program were more complex and contained another file, we would need to first run javac HelloWorld.java, to compile, followed by java HelloWorld.java.