What is called a forward reference in Java?

Question

I have been through this question on legality of forward references but not clear as to what is meant by forward references in Java language . Can someone ple

Answer 1

public class AnyCode {

    void print() {
        System.out.println("Value of j - " + j);   // legal
        System.out.println("Value of i  - " + i);  // legal
    }

    // CASE - 1 
    int k = i;         // illegal
    int i; 

    // CASE - 2 
    int l = j;         // legal
    static int m = j;  // illegal
    static int j;

    // CASE - 3 
    A aObj = bObj;     // illegal
    B bObj = new B();

    public static void main(String[] args) {

        /* 
           Note :- here anyCode act as a local variable and get space on stack 
           whereas the object it is referring to is present on heap. And you 
           cannot forward reference a local variable. 
        */

        anyCode.print();    // 'Cannot find symbol' error
        AnyCode anyCode = new AnyCode();
    }

}

class A {

}

class B {

}

*********Refer CASE - 1*********

Forward referencing instance variable is not allowed as compiler is not sure of the type of value we are forward referencing or it might even be possible that no such variable exist.

Consider an example :-

int a = b;
boolean b = false;

If forward referencing is allowed in above case then it might create a havoc.

int a = b; // What is b? is it a primitive variable or a value or a object reference

in the above example i have decided not to declare b and now if such assignment were allowed by java, then it will be a nightmare.

**********Refer CASE - 2*********

Static variables are loaded before instance variables and hence forward referencing static variables and assigning them to instance variable is perfectly fine