Sending array index by reference

Hi there:

Could anyone please tell me how to send an array index to a method by reference? I want to do something like this:

void foo1()
{
int[] arr = { 1,2,3,4,5 };
foo2( arr + 1 ); //It gives me a compile error here
}

void foo2( int[] arr )
{
arr[0] ++;
}

In C++ I'd simply call foo2 from foo1 like this:
foo2( arr + 1 );
OR
foo2( &arr[ 1 ] );

Any help would be appreciated.

An array index is an int which is a primitive, primitives don't have references, and Java is pass-by-value and pass-by-value only. If you want to change what an array contains in a specific index than either have the method return the new object and assign the element to the array from outside the method, or pass the array reference value and the index as parameters to the method.

Hi:

But I'm not sending an int over to foo2, I'm sending an array of integers to foo2. I only want to change the start index of the array, i.e. I want to send the array starting from index 1.

Then pass the array and an index (to start from).

Edit: So, what part of

Quote:

---

Originally Posted by masijade

If you want to change what an array contains in a specific index than either ..., or pass the array reference value and the index as parameters to the method.

---

There are limitations in my program and I'm not able to change the argument list...

Then you are going to have to change the array that you're passing. copy it, shifting the positions, and copy it back when you're done. Or rethink what it is you're doing and how you're doing it.

What exactly are you trying to do that you feel the need to do it this way.

Thanks for the suggestions. However, I'm not able to copy a whole array just because of this and am looking for a better solution. I have a recursive method that will pass an array that starts from the next index every time. I could do that very simply in C++, so I'm assuming there's got to be a way to do it in Java too. After all, an array name is just a pointer pointing to the first index, and all I want is to point it to the next index...

That's why you need to tell it what index to point to by passing that index as an argument. If you are unwilling (or,as you claim unable) to do that it is not my fault, nor the fault of the language.

Quote:

---

Originally Posted by mattie

void foo1()
{
int[] arr = { 1,2,3,4,5 };
foo2( arr + 1 ); //It gives me a compile error here
}

void foo2( int[] arr )
{
arr[0] ++;
}

---

C and C++ have pointer arithmetic; a lovely little feature that ruins static type safety checks and causes a lot of trouble in the hands of the inexperienced; Java doesn't have that. You have to change your method foo2( ... ) to:

Code:

---

void foo2(int[] arr, int i) {
  arr[i]++;
}

---

... or do as Masijade suggested: copy part of the array over to another one and use that (a rather expensive hack). Changing code from C or C++ when it uses pointer arithmetic can be a burden ...

kind regards,

Jos

Already suggested also, claims he can't change the method declaration.

Quote:

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Originally Posted by masijade

Already suggested also, claims he can't change the method declaration.

---

Ah, I missed that; sorry about that; well, the OP is out of luck then (or he has to implement that silly array copy hack ;-)

kind regards,

Jos

I have no problems with it. Feel free to hack away at me! ;-)

Thanks guys. I'm a "she" by the way, lol!
This sucks then... What is the object type of an array? Could I somehow use type casting, or operator +, etc.?

Quote:

---

Originally Posted by mattie

This sucks then... What is the object type of an array? Could I somehow use type casting, or operator +, etc.?

---

It doesn't suck; you're trying to transform a piece of code from one language to another; one language has pointer arithmetic, the other one doesn't. There's no way you can trick it into it with obscure use of operators ... It doesn't have pointer arithmetic.

kind regards,

Jos

How are you going to do recursion with a void method anyway?

-Gary-