Re: Can arrays be parameters to generics
Lew wrote:
Your example contrasts arrays with Sets. That is an apples-to-oranges
comparison. Sets have different logical characteristics than arrays;
Some folks think of Maps as "the other array" -- associative arrays.
Why the heck he's got Sets in there I'm not really sure. Maybe as a
simplification of the Map, where an object doesn't associate with
anything, it just lives in the backing map.
Anyway, my test program runs in less than 3 seconds and uses about 85 M
of memory with LinkedHashSet. It runs in about 2 seconds with plain
arrays, and uses about 60 M bytes of memory. Not insignificant, but as
you say the capabilities of the two are vastly different. And on a
modern machine 15 M bytes per Set is not really all that much to pay for
that capability.
(Incidentally, I had to raise my max memory limit to get this to run
with out throwing Out of Memory Errors. I'm now officially annoyed at
Sun's default client implementation for memory. Why not just use what
memory is available? It's the expected behavior for every other app on
my desktop. Why does Java go out of it's way to be different in
annoying ways?)
package arraytest;
import java.util.Arrays;
import java.util.LinkedHashSet;
import java.util.Set;
public class Main {
private static final int NUM = 1000000; // 1 million
public static void main(String[] args) {
test2();
}
static void test1()
{
Set<String> test = new LinkedHashSet<String>();
for( int i = 0; i < NUM; i++ ) {
test.add( "test string " + i );
}
System.out.println("Total capacity: " + test.size() );
System.out.println("Hascode: "+ test.hashCode() );
}
static void test2()
{
String test2 [] = new String[NUM];
for( int i = 0; i < NUM; i++ ) {
test2[i] = "test string " + i;
}
System.out.println("Total capacity: " + test2.length );
System.out.println("Hascode: "+ Arrays.hashCode( test2 ) );
}
}