As I understood null is instance of T for all reference type T.
Question 1. What's defenition of null? How does null represents in memory?
Consider the following case: We defined class
public class MyClass{
Integer i;
}
Now null can be cast to MyClass, but I don't explicitly define that.
Question 2. From what compiler will be know that null can be cast to MyClass?
Formally, null is a singleton member of the null type, which is defined to be the subtype of every other Java type.
null is a reference type and its value is the only reference value which doesn't refer to any object. Therefore there is no representation of null in memory. The binary value of a reference-typed variable whose value is null is simply zero (all zero bits). Even though this is not explicitly specified, it follows from the general initialization semantics of objects and any other value would cause major problems to an implementation.
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