Array length of a long value

[Naveg]

Is it at all possible to have an array that has a length of a long value?? So far all my research has shown that only ints can be the index of an array....

If not, how would I go about storing a "long" number of things?

[wtd]

ArrayList also appears to be limited to "int" length.

I'd suggest reconsidering why you're storing that much at one time. That would be using massive amount of memory.

[Naveg]

well, i have an assignment to find all the primes up to an inputted number...and i thought i would use the sieve of eratosthenes. Use a boolean array, start all at true, gradually eliminate composite numbers, output all remaining "true" indexes

[wtd]

Do you expect such a large input number?

[Naveg]

My teacher said to use longs so he can test the efficiency with larger numbers.

[wtd]

Then you may have to try a different strategy.

[Naveg]

Well...would there be any other way to implement the sieve of eratosthenes without using an array?

[beard0]

Naveg wrote:

Well...would there be any other way to implement the sieve of eratosthenes without using an array?

No. You could however use the sieve of eratosthenes using a two dimmensional array where

code:

virtualArray[longValue] = actualArray[longValue / maxInt][longValue % maxInt]

[GlobeTrotter]

What about using a linked list?

[rizzix]

GlobeTrotter wrote:

What about using a linked list?

That would slow the algorithm down... the faster alternatives would be ArrayList or Vector.. but then again.. i think they too fall under the same restriction.

[wtd]

rizzix wrote:

GlobeTrotter wrote:

What about using a linked list?

That would slow the algorithm down... the faster alternatives would be ArrayList or Vector.. but then again.. i think they too fall under the same restriction.

They do.

[Naveg]

how then do people have programs that can find primes up to massively huge numbers like 100000000000 using the sieve of eratosthenes? Do they not use arrays?

I'm researching a different algorithm for finding primes to try and accomodate a larger range of values without sacrificing speed....

[wtd]

Naveg wrote:

how then do people have programs that can find primes up to massively huge numbers like 100000000000 using the sieve of eratosthenes? Do they not use arrays?

They don't use Java?

[Naveg]

wtd wrote:

Naveg wrote:

how then do people have programs that can find primes up to massively huge numbers like 100000000000 using the sieve of eratosthenes? Do they not use arrays?

They don't use Java?

Figured you'd say that. But in a language like C++, do arrays take up less RAM? Or are the other data structures in C++ just far faster than those of Java?

[wtd]

Well, in C and C++, the problem is that arrays are glorified pointers. On a 32-bit machine, array indexes can only be 32-bit integers.