Why it prints zero and not null

When we do not initialize a variable and access it from an object why does it print as zero....why doesn't it display null
Like in the below program

public class Test{
int i;
public static void main(String[] args) {
Test t = new Test();
System.out.println(t.i);
}

}

[color=#FF0000:j6iet16c]Why output display as zero, why it does not display as null?[/color:j6iet16c]

Thanks,
Ravi