Why Java does not allow null while declaring primitive data types [duplicate]

Answer 1

Because primitives represent value and Object variables represent references (something like pointers) to complex data objects. There is no null value general, it is a special keyword that "references to nothing" or empty reference - this is highly unprofessional answer, but I guess it will be most appropriate.

Besides, what could be in your opinion, numerical value of null? 0? -1? But, those are valid integers so what else?

I strongly suggest that you start familiarizing yourself with the following complex java tutorial. Every aspect that you have been asking about is explained there and supported with examples.

Answer 2

The reference values (often just references) are pointers to these objects, and a special null reference, which refers to no object.

As per jls-4.3.1, it is pointless to take about the null reference without the existence of an object.

Answer 3

Objects like Character and Integer are pointers: the actual number stored in the bytes that are that variable's value represents an address in memory for the rest of the JVM's memory. So, it is possible and meaningful to set that number to an address that goes nowhere, which is what null is.

A primitive like int or char, however, has a number that is interpreted as a number (integer, or ASCII code), and there's no way to make it "not a number" because all that the memory can possibly store is numbers.

Answer 4

null means "lack of an object". References can lack an object, primitives can't.

Answer 5

Java primitive type variables are store-by-value instead of store-by-reference variables. Where as the wrapper classes are objects basically like any other Java object except that all they do is wrap a primitive type.

Answer 6

Along with all above answer i would like to add this point too.

For primitive types,we have fixed memory size i.e for int we have 4 bytes and char we have 2 bytes. And null is used only for objects because there memory size is not fixed.

So by default we have,

   int a=0;

and not

   int a=null;

Same with other primitive types and hence null is only used for objects and not for primitive types.