Question

I am writing a simple program:

class Demo{
    public static void main(String[] args){
        system.out.println("Hello");
    }
}

on compilation it gives an error: package system not found.
Why it do so that package not found instead system is a misspelled class name.

Answer 1

Why it do so that package not found instead system is a misspelled class name

When you say something.somethingElse the compiler assumes you are doing a packageName.classname. In this case you were intending to access out of the System class, but you could very well be trying to access a package called system that is not present (in the classpath for instance). So it is a guess from a compiler.

And (I guess) it is so because this is the better guess. Let’s say the compiler said class not found. You might be happy. But tons of others doing Java.util.List (instead of java.util.List) would complain “I was trying to access the java.util package but misspelled it. The compiler wrongly says Missing class name.

Update (for the sake of completeness)
From @paxdiablo’s answer below:

The reason why the compiler is assuming it’s a package name rather
than a class or variable name lies in section 6.5 of the JLS,
“Determining the meaning of a name”