Bob Martin prime generator

PrimeGenerator3.java

package com.hollandandbarrett.tpl.literatePrimes;

public class PrimeGenerator3 {
    private static int[] primes;
    private static int[] primeMultiples;
    private static int lastRelevantMultiple;
    private static int primesFound;
    private static int candidate;

    // Lovely little algorithm that finds primes by predicting
    // the next composite number and skipping over it. That prediction
    // consists of a set of prime multiples that are continuously
    // increased to keep pace with the candidate.

    public static int[] generateFirstNPrimes(int n) {
        initializeTheGenerator(n);

        for (candidate = 5; primesFound < n; candidate += 2) {
            increaseEachPrimeMultipleToOrBeyondCandidate();
            if (candidateIsNotOneOfThePrimeMultiples()) {
                registerTheCandidateAsPrime();
            }
        }
        return primes;
    }

    private static void initializeTheGenerator(int n) {
        primes = new int[n];
        primeMultiples = new int[n];
        lastRelevantMultiple = 1;

        // prime the pump. (Sorry, couldn't resist.)
        primesFound = 2;
        primes[0] = 2;
        primes[1] = 3;

        primeMultiples[0] = -1;// irrelevant
        primeMultiples[1] = 9;
    }

    private static void increaseEachPrimeMultipleToOrBeyondCandidate() {
        if (candidate >= primeMultiples[lastRelevantMultiple])
            lastRelevantMultiple++;

        for (int i = 1; i <= lastRelevantMultiple; i++)
            while (primeMultiples[i] < candidate)
                primeMultiples[i] += 2 * primes[i];
    }

    private static boolean candidateIsNotOneOfThePrimeMultiples() {
        for (int i = 1; i <= lastRelevantMultiple; i++)
            if (primeMultiples[i] == candidate)
                return false;
        return true;
    }

    private static void registerTheCandidateAsPrime() {
        primes[primesFound] = candidate;
        primeMultiples[primesFound] = candidate * candidate;
        primesFound++;
    }
}