Can't figure out what's causing this error "This class does not have a static void main method accepting String[]."

I have a college assignment to practice with testing methods in Java, I can't figure out why I'm getting the error, "This class does not have a static void main method accepting String[]." I'm using Dr. Java and another thing to note is I'm very new to programming so the solution may be rather obvious.

Main class file.

public static void displayLine() //Displays line
{
System.out.println("--------------------"); //print line
}
public static void displayMessage(String message) //show message 
{
System.out.println(message); //display message
}
public static int sumNumbers(int num1, int num2) //method for returning the sum
{
return (num1 + num2); //add the two numbers
}
public static boolean isGreater(int num1, int num2) //see if the number is greater.
{
boolean isGreater; 
if (num1 > num2) //conditional statement to see which number is larger
{
isGreater = true;
} else {
isGreater = false;
}
return isGreater; //returns whether or not it is greater
}
public static void setBulb(boolean state) //determines if bulb is on or off
{
if (state == false) //conditional statemtnt to show whether the bulb is on or off.
{
System.out.println("The bulb is now off");
} 
else 
{
System.out.println("The bulb is now on");
}
//^^^ I could not get this to work. I wonder if it is because I didn't create a new instance of the method???
}

Second class file.

public static void main (String[] args)
{
HaaKaMethodsPractice testMethods = new HaaKaMethodsPractice(); // Create a new instance of the MethodsPractice class.
//^^^I could not get this statement to work.
// Test the displayLine method.
testMethods.displayLine(); // Display a line.
// Test for the setBulb method
boolean state = true; // Initial value for the boolean sent to test this method.
testMethods.setBulb(state); // Invoke the setBulb method and pass it a boolean of true.
state = false; // Change the boolean 'state' to false, and test again.
testMethods.setBulb(state); // Invoke the setBulb method.
testMethods.displayLine(); // Display a line.
// Test for the displayMessage method.
String message = "This book is in stock."; // Set a value to be sent to the method.
testMethods.displayMessage(message); // Invoke the displayMessage method and send the message.
testMethods.displayLine(); // Display another line.
// Test for the sumNumbers method.
int num1 = 7; // Give num1 an initial value.
int num2 = 5; // Give num2 an initial value.
int totalOfNumbers = 0; // Set the initial value to 0.
totalOfNumbers = testMethods.sumNumbers(num1, num2); // Set a variable to hold the returned value and send the numbers.
System.out.println("The total of the two numbers is: " + totalOfNumbers); // Display the result to see if it is correct.
testMethods.displayLine(); // Display another line.
// Test for the isGreater method. Uses num1 and num2 from previous method.
boolean greater = false; // Give an initial value to boolean greater.
greater = testMethods.isGreater(num1, num2); // Set a variable to hold the returned value and send the numbers.
System.out.println("First number greater? " + greater); // Display the results to see if they are correct.
testMethods.displayLine(); // Display another line.
testMethods.displayLine();
}

You don't create 'instances of a method'. You create instances of a class. And that method you put that comment under is a static method. static can be confusing at times, and tends to lead you straight into a model of thinking about your code that clashes with how java works best, so, stop using static. I suggest your main method contains one single line of code: new MyThingie().go(args);, where you can leave out the args if you aren't going to use the command line args, and go is the actual real 'main' method (and is not static). That's because main has to be static, but that should be the only static thing in your code base until you're many weeks into your java career.

As to the error: You are running a class or source file. The one you're running? That one needs to have that public static void main(String[] args) method.

For example, setBulb being static is rather illogical. That would presume there is only one bulb on the entire planet and even the concept of 'two bulbs' is non-sensical (imagine the concept of 2 'sense of existence' - some things do not come in amounts, they just are. That's what static methods are like. The concept of adding numbers? That's not subject to the concept of amounts. But bulbs are, so setBulb definitely should not be static, just an example).