Fix Java Error Could not find or load main class

When starting to learn JAVA, everyone goes through their first HelloWorld program, learning to compile HelloWorld.java using javac and java commands in Command Prompt (CMD). You might encounter this error: "Error: Could not find or load main class HelloWorld". Fixing this Java error is very simple as it is a syntax mismatch error.

How to Fix Java "Error: Could not find or load main class HelloWorld"

When running javac, no error appears, but running java afterwards produces the following output:

C:\Users\DoAh\Desktop\Java_Workspace>javac HelloWorld.java
C:\Users\DoAh\Desktop\Java_Workspace>java HelloWorld
Error: Could not find or load main class HelloWorld
C:\Users\DoAh\Desktop\Java_Workspace>

You need to change the class name to match the .java file name.

Example:

Inside file HelloWorld.java, you have the following code:

class HelloWorldApp {
  public static void main(String[] args) {
    System.out.println("Hello World!"); // Display the string.
  }
}

When you execute javac HelloWorld.java, Java creates a compiled file named HelloWorldApp.class (using the class name as the output filename).

Therefore, when you subsequently execute java HelloWorld, it throws "Error: Could not find or load main class HelloWorld" because HelloWorld.class does not exist.

To fix it, rename the file to HelloWorldApp.java or execute java HelloWorldApp instead.