Static Methods

[nhmllr]

From what I understand, not static methods can only be used directly by the instance under which the method exists. However, a static method can be accessed with the class name, not the instance name. Tell me if my understanding's wrong.

Now, I'm working through project euler (really great, check it out if you haven't) and all of the problems are solvable with one class that has a main() in it. However, I like to make methods to organize my thoughts, so I put some methods inside of the class. The compiler would only accept them if they were static, though. Why would that be? Why can't I make methods that are not static in this situation?

Here's a silly example I just made up:

public class example {
	//main
	public static void main(String[] args) 
    {
		int number = 1;
		System.out.println(triple(number));
    }
	
	public static int triple(int n)
	{
		return 3*n;
	}
}

If triple() isn't static, it won't compile. Why not? Shouldn't a method always be able to be called from within itself?

Thanks

[Guy]

It has to be main because you're calling it from the static main method. If you don't want it to be static, call it from the constructor like this:

public class example {

    public example{
        System.out.println(triple(number));
    }
    //main
    public static void main(String[] args) 
    {
        int number = 1;
        new example();
  
    }
     
    public int triple(int n)
    {
        return 3*n;
    }
}

Hope thats helpful.

[JosAH]

It has to be main because you're calling it from the static main method. If you don't want it to be static, call it from the constructor like this: [ ... ]

Hope thats helpful.

No it isn't because your code doesn't even compile. A non-static method can only be called against a target object, i.e. the object that has to execute the body of that method. No object, no method; it's that simple. A static method needs a target, an object somewhere to call a non-static method against. If it hasn't a target object, it can't call that non-static method.

kind regards,

Jos

[Guy]

My bad, thanks for correcting me!
I guess I'm still to much of a newbie to be helping :P
This is what I meant to write though. which does compile:

public class numbers {

public numbers() {
int number = 1;
System.out.println(triple(number));
}
//main
public static void main(String[] args)
{
new numbers();
}

public int triple(int n)
{
return 3*n;
}
}