Does Java support pointers?

[kthaker]

Hi All,

I would like to know whether Java supports pointers or not..As far as I know it does not have pointers but I don't know the exact reason why it do not support. Please let me know the reason.

Thanks.

[pbrockway2]

I would like to know whether Java supports pointers or not.

Yes and no.

You can't do anything with memory addresses in Java. Including, notably, pointer arithmetic of the *p++ variety.

You can dereference things - indeed it's hard to do anything nontrivial without using the dot operator. The things you dereference are variously called "references" (very helpful!) and "pointers to objects" (see for example the JLS 4.3.1). This latter description gets at the fact that Java's foo.bar() somewhat resembles (*foo).bar() or foo->bar().

Please let me know the reason.

I have no idea about this. Who would, except for the language's authors? Maybe someone has a link to an account of what caused or motivated them to act as they did.

[quad64bit]

Object references are treated like pointers where as primitives are passed by value. Direct memory addressing makes little sense in a virtual environment, which java is.

public void test(){
        Ob a = new Ob();
        Ob b = a;
        a.val++;
        System.out.println(b.val);
}

class Ob{
    public int val = 4;
}

If in this case java was not using a pointer (pass by value), we would expect the print out to be 4, since b was initialized with a's value. Since b is actually a reference to a itself, incrementing a's value also affects b. Note that this is not true with primitives, Strings, or the primitive wrapper classes.

I use the term point somewhat loosely since in java (as I mentioned) you cannot deal with actual memory addresses directly, however, if pointer is defined as multiple fields 'pointing' at the same memory location, then java does use 'pointers' for objects.