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behar
10,799 PointsJava, non main class cant call certain functions?
Why is it that outside the main class, i cannot call System.out.prinln() without putting it inside a method.
A simple but detailed explanation would be appreciated!
1 Answer
Paolo Bass
3,921 PointsHi behar,
When you mention 'main class', I assume that you are talking about this:
public static void main(String[] args){}.
This is not a class. It is a method (or function if you rather), as indicated by the 'void' rather than a 'class'. You can only call code from inside of a method, and System.out.println() is a call to a method called println(). This is the case with ALL methods, not just the println() method.
The reasoning for this is that, outside of a method, no code will run. Think of methods as a sort of chain reaction. All methods can only be called from inside of another method, and the chain starts from the 'main method'. Therefore, calling any method in a location that is outside of another method will result in it never running, as it can never be reached from the main method (which is the starting point of the program), and the computer doesn't know when to call it.
Certainly, you can create and initialise variables from outside of methods, however this code only ever runs once, when the program first starts. It doesn't need timing specificity. It therefore doesn't need to be called in a certain order and it never has to be called again, hence the reason why it does not need to be located inside of a method.
Of course, you can create and initialise variables from inside methods, and doing so will indicate that those variables are needed during specific points in the 'method chain'.
I hope this helped.