Euler 10

Euler10.java

import java.util.BitSet;

public class Euler10 {
	private static BitSet runSieve(int limit) {
		BitSet bits = new BitSet(limit+1);
		int sievingLimit = (int)Math.ceil(Math.sqrt(limit));
		for(int n = 2; n <= limit; n = bits.nextClearBit(n+1)) {
			if(n > sievingLimit) break; // any composites will be past the limit
			for(int m = n*n; m > n && m <= limit; m += n) {
				bits.set(m, true);
			}
		}
		
		return bits;
	}	
	
	/**
	 * @param args
	 */
	public static void main(String[] args) {
		long start = System.currentTimeMillis();
		
		int limit = 2000000;
		BitSet sieve = runSieve(limit);
		long sum = 0;
		for(int n = 2; n < limit; n = sieve.nextClearBit(n+1)) {
			sum += n;
		}
		
		System.out.println("Took " + (System.currentTimeMillis() - start) + "ms");
		System.out.println("Result: " + sum);
	}

}

results

Took 27ms
Result: 142913828922