Recursive Prime Sieve Class

Primes.java

public class Primes {
  public static void main(String[] args) {
    //Print the primes up to 107.
    for (Integer p : new RPrimeSieve(107))
      System.out.println(p);
  }
}

RPrimeSieve.java

package primes;

import java.util.Iterator;

class RPrimeSieve implements Iterable<Integer> {
  private Integer prime;
  private Boolean[] sieve;

  public RPrimeSieve(Integer max) {
    this(2, initSieve(new Boolean[max+1]));
  }

  private RPrimeSieve(Integer p, Boolean[] sieve) {
    this.sieve = sieve;
    prime = nextPrime(p);
  }

  private static Boolean[] initSieve(Boolean[] sieve) {
    for (Integer i = 2; i < sieve.length; i++)
      sieve[i] = true;
    return sieve;
  }

  private Integer nextPrime(Integer p) {
    for (Integer i = p; i < sieve.length; i++)
      if (sieve[i])
        return i;
    return sieve.length+1;
  }

  private RPrimeSieve next() {
    if (prime < sieve.length) {
      markMultiples(prime);
      return new RPrimeSieve(this.prime, sieve);
    }
    return null;
  }

  private void markMultiples(Integer n) {
    for (Integer i = 1, j = n; j < sieve.length; i++, j = i*n)
      sieve[j] = false;
  }

  public Iterator<Integer> iterator() {
    final RPrimeSieve that = this;
    return new Iterator<Integer>() {
      private RPrimeSieve cur = that,
                          next;

      public void remove() { throw new UnsupportedOperationException(); }
      public boolean hasNext() {
        next = cur.next();
        return next != null;
      }
      public Integer next() {
        Integer r = cur.prime;
        cur = next;
        return r;
      }
    };
  }
}

Thank you for writing this useful program.