Java, Create array if it doesn't already exist

I couldn't find anything on that while googling so I want to create an array only if it doesn't already exists.

EDIT: I mean not initialized

I know how to check for values in the array

Should be simple but I'm stuck

best regards

static long f(long n) {
    int m = (int)n;
    **if (serie == null) {

   long[]开发者_Python百科 serie = new long[40];
    }**
    if (n == 0) {
        return 0;
    }
    else if (n==1) {
        return 1;
    }
    else {
        long asdf = f(n-1)- 2*(f(n-2)) + n;
        return asdf;
    }
}

something like that a recursive function and I want to save the values in an array

You are trying to use the serie array but it is not yet declared. First declare it and then use it, as you want.

Are you looking for:

if (values == null)
{
    values = new int[10];
}

or something like that? If not, please edit your question to provide more information.

EDIT: Okay, judging by the updated question, I suspect you ought to have two methods:

static long f(long n)
{
    return f(n, new long[40]);
}

static long f(long n, long[] serie)
{
    // Code as before, but when you recurse, pass in serie as well
}

(Note that your current code doesn't use serie at all.)

if(array==null){
//create new array
}

AFAIK, there are, if you use a variable in java, it is initialized. So you probably want to check if that variable, an array in this case, is null. Not only that, you can and probably should check if it is an array. Arrays are objects in java. So you could do something like this for an array:

if(!obj.getClass().isArray())