JavaOne Talk: Ruby Prime Sieve

See this post for an explanation on why this code is being shown and what kind of responses would be useful. See this post for the Java algorithm to compare against.

class RubyPrimes
  attr_accessor :cnt, :primes
  def initialize(n)
    @primes = Array.new(n,0)
    @cnt = 0
    i = 2
    max = calcSize
    nums = Array.new(max,true)
    while (i < max && @cnt < @primes.length)
      p = i
      if (nums[i])
        @primes[@cnt] = p
        @cnt += 1
        (p .. (max/p)).each{ |j| nums[p*j] = false }
      end
      i += 1
    end
  end
  def calcSize
    max = 2
    max = max * 2 while ( max/Math.log(max) < @primes.length)
    max
  end
  def last
    @primes[@cnt -1]
  end
end