Initial values to instance & class variable

Question

I read in the book that instance & class variable definitions are given an initial value depending on the type of information they hold:
Numeric variable - 0
Characters - '\0'
Boolean - false
Objects - null
But when I try to compile a class without giving explict value to the variable I get error.
So why do I need this initial value - if it can't be used any way?

Answer 1

Sorry� I'll try to make my question clearer.
As I wrote in my previous message, I read in the book that instance & class variable definitions are given an initial value depending on the type of information they hold:
Numeric variable - 0
Characters - '\0'
Boolean - false
Objects - null
From the above I understand that whenever I declare a variable without assigning it a value, it automatically has an initial value.
For example:
Class Myclass(){
Int x;
Static int z;
Void fooMyClass(){
Int y;
I understand from what I read in the book, both x, y & z - get default values of zero. Is that correct?
if it is correct, why can't I use these values that were assign as default?