December 12, 2012 15:01 · Dec 12, 2012
diff --git a/gistfile1.txt b/gistfile1.txt
@@ -0,0 +1,43 @@
+public class OnesFunction {
+
+  private static LoadingCache<Integer, Integer> cache = CacheBuilder
+			.newBuilder().maximumSize(1000)
+			.expireAfterAccess(10, TimeUnit.MINUTES)
+			.build(new CacheLoader<Integer, Integer>() {
+				@Override
+				public Integer load(final Integer i) throws ExecutionException {
+					return countOnes(i);
+				}
+			});
+
+	/**
+	 * @param args
+	 * @throws ExecutionException 
+	 */
+	public static void main(String[] args) throws ExecutionException {
+		int i = 2;
+		while (true) {
+			final int n = countOnes(i);
+			System.out.println("" + i + ":" + n);
+			if (i == n)
+				break;
+			i++;
+		}
+	}
+
+	public static int countOnes(final int i) throws ExecutionException {
+		if (i == 0)
+			return 0;
+		return internalCountOnes(i) + cache.get(i - 1);
+	}
+
+	private static int internalCountOnes(final int i) {
+		final String s = String.valueOf(i);
+		int sum = 0;
+		for (final char c : s.toCharArray())
+			if (c == '1')
+				sum += 1;
+		return sum;
+	}
+
+}