How to Compile and Run your Java Program in Command Line

In this tutorial, we are going to see how to write, compile and run a java program. Compiling and running a java program are very easy tasks to perform after installing JDK. Here are the steps:
 

Java program:

public class MyClass 
{
  public static void main(String[] args)
  {
    System.out.println("Welcome To StackHowTo!");
  }
}

Output:

Welcome To StackHowTo!

 

How to compile and run the above program

Step 1: Open a text editor, like Notepad on Windows, and TextEdit on Mac. Copy the above program and paste it into the text editor.

You can also use an IDE like Eclipse to run the java program but we will see this part in the next tutorials. To keep things simple, we’ll only be using the text editor and the command prompt (or terminal) for this tutorial.

Step 2: Save the file as MyClass.java. You might be wondering why we named the file as MyClass, the point is, we always have to name the file the same as the name of the public class. In our program, the name of the public class is MyClass, that’s why our filename must be MyClass.java.
 

 
Step 3: In this step, we’ll compile the program. To do this, open the Command Prompt (CMD) in Windows, if you are on Mac OS, open Terminal.

To compile the program, type the following command and press Enter.

javac MyClass.java

 

If you get this error, you must first set the path before compilation.
 

 

Define the path in Windows:

Open Command Prompt (CMD), go to where you installed java on your system, and locate the bin directory.
 

 
Copy the full path and write it in the command line like this.

set path=C:\Program Files\Java\jre1.8.0_121\bin

 

Define the path in Mac OS X:

Open the Terminal, type the following command and hit return.

export JAVA_HOME=/Library/Java/Home

Type the below command on the terminal to confirm the path.

echo $JAVA_HOME

Step 4: After compilation, the .java file is translated to the .class file (byte code). We can now run the program. To run the program, type the below command and press Enter:

java MyClass

 
You will be able to see the result displayed on the output.

Note that you should not add the .java extension to the file name when running the program.
 

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