How to simulate the Out Of memory : Requested array size exceeds VM limit

I used the Out Of Memory help from sun's site. Where it is quoted as

Out Of Memory : Requested array size exceeds VM limit

This indicates that the application attempted to allocate an array that is larger than the heap size. For example, if an application tries to allocate an array of 512MB but the maximum heap size is 256MB, then this error will be thrown. In most cases the problem is likely to be either that the heap size is too small or that a bug results in the application attempting to create an array whose size is calculated to be incorrectly huge.

I tried to simulate this by

import java.util.ArrayList;
import java.util.List;

public class JavaTest {
    public static void main(String[] args){
        long[] ll = new long[64*1024*1024];
    }
}

on my machine with

javac *.java;java -Xmx256m JavaTest

But the above line is producing

Exception in thread "main" java.lang.OutOfMemoryError: Java heap space
    at JavaTest.main(JavaTest.java:7)

What am I missing?

Update : My java version is

$java -version
java version "1.6.0_15"
Java(TM) SE Runtime Environment (build 1.6.0_15-b03)
Java HotSpot(TM) Server VM (build 14.1-b02, mixed mode)