How do I check if a variable has been initialized

Question

First of all, I'm fairly new to Java, so sorry if this question is utterly simple.

The thing is: I have a String[] s made by splitting a String in which every item is a number. I want to cast the items of s into a int[] n.

s[0] contains the number of items that n will hold, effectively s.length-1. I'm trying to do this using a foreach loop:

int[] n;
for(String num: s){
    //if(n is not initialized){
        n = new int[(int) num];
        continue;
    }
    n[n.length] = (int) num;
}

Now, I realize that I could use something like this:

int[] n = new int[(int) s[0]];
for(int i=1; i < s.length; i++){
    n[i-1] = (int) s[i];
}

But I'm sure that I will be faced with that "if n is not initialized initialize it" problem in the future.

Answer 1

You can't cast a String to an int. Java is strongly typed, and there is no implicit type conversion like you might find in a scripting language.

To convert a String to an int, use an explicit conversion, like Integer.parseInt(String).

All member variables and elements of arrays are initialized with a default value. For int types, the value is 0. For reference types (any subtype of Object), the default value is null. Local variables don't get a default value, but the compiler analyzes the code to ensure that a value is assigned before the variable is read. If not, the code will not compile.

I think what you want is something like this:

int[] n = new int[Integer.parseInt(s[0]);
for (int idx = 0; idx < n; ++idx)
  n[idx] = Integer.parseInt(s[idx + 1]);