What does the Java compiler error message "<identifier> expected" mean?

class if{
    public static void main (String args[]){
        int x = 9;
        if (x <= 9){
            System.out.println("Yay")开发者_如何学C;
        }else{
            System.out.println("Yay");
            }
        }
    }

I'm running this from the compiler, using Notepad++ as the text editor. And I am getting an error in the compiler saying <identifier> expected class if. And another error saying illegal start of expression. As well as saying error ";" expected. I have a total of 9 errors.

I made sure to match all the {} and (). Even scraped the program and tried again with the same results.

if is a reserved keyword in Java (as seen in your if statement), and is thus not an eligible class name. Choose another name for your class, like IfTesting.

By convention, all class names start with an upper-case letter. The full details for what is and isn't a valid Java identifier are found in the Java Language Specification. In short, it can't be a keyword, true, false, or null.

You shouldn't call a class "if". It's a reserved Java keyword (that you're using in your program, BTW).

Furthermore, by convention, all classes start with an uppercase letter in Java.

You cannot name your class or even a variable with a keyword.

You can't name your class if, as it's a keyword. Check this for more examples.

Also, it's (String[] args)

Not (String args[])