Basic Java homework

Question

I know this is simple but I don't really understand the question...

Assume the signature of the method xMethod is as follows. Explain two different ways to invoke xMethod:

public static void xMethod(double[] a)

I thought to invoke a method you just do:

xMethod(myarray);

What could it mean by asking two different ways? Maybe I'm just looking into the question too much.

Answer 1

For kicks, show your professor this:

XClass.class.getMethod("xMethod", a.getClass()).invoke(null, a);

Then tell them the two answers are

XClass.xMethod(a);
//and
xObject.xMethod(a); //this is bad practice

Answer 2

If this is for a first time java class, my guess is he is looking for these 2 cases:

//the one you have, using a precreated array
double[] myArray = {1.1, 2.2, 3.3}
xMethod(myarray);

//and putting it all together
xMethod(new double[]{1.1, 2.2, 3.3});

Basically illustrating you can make an array to pass, or simply create one in the call.

Just a guess though

Answer 3

You could invoke it either by calling it on a class, or via an instance of that class.

Foo.xMethod(a);

or:

Foo foo = new Foo();
foo.xMethod(a);

The first approach is prefered, but the second one will compile and run. But be aware that it is often considered a design flaw in the language that the second approach is allowed.

Answer 4

static methods are not bound to the construction of the class. The method above can be called either by constructing the class or just by using the namespace:

Classname myclass = new Classname();
myclass.xMethod(myarray);

or you could just do:

Classname.xMethod(myarray);

as you see, you don't have to construct the class in order to use the method. On the other hands, the static method can't access non-static members of the class. I guess that's what the question meant by 2 different ways...