Stock System In Java

I'm making a stock system for the heck of it,so everything was going great until I hit the loop I am trying to use a for loop to add stock to the stock system,any way the question is maily about loops.How come I cannot declare a variable outside a loop and assign a value to it,for example I can declare as follows and I will not get an error,

for(int i=0;i<10;i++){
System.out.println("example");

}

but in my code(and yes its the only error I get I tested it) I get an error and can only declare and assign a value inside the loop,the reason for this is because I wanted to get the value from another class and use it in the loop ok so heres the code from both classes.

public class mainn{

public static void main(String [] args){
stock first = new stock();
int internal;
internal = first.wanted;

[code]....