Initial data commit

Task/Primorial-numbers/Java/primorial-numbers.java

@@ -0,0 +1,45 @@
+import java.math.BigInteger;
+
+public class PrimorialNumbers {
+    final static int sieveLimit = 1300_000;
+    static boolean[] notPrime = sieve(sieveLimit);
+
+    public static void main(String[] args) {
+        for (int i = 0; i < 10; i++)
+            System.out.printf("primorial(%d): %d%n", i, primorial(i));
+
+        for (int i = 1; i < 6; i++) {
+            int len = primorial((int) Math.pow(10, i)).toString().length();
+            System.out.printf("primorial(10^%d) has length %d%n", i, len);
+        }
+    }
+
+    static BigInteger primorial(int n) {
+        if (n == 0)
+            return BigInteger.ONE;
+
+        BigInteger result = BigInteger.ONE;
+        for (int i = 0; i < sieveLimit && n > 0; i++) {
+            if (notPrime[i])
+                continue;
+            result = result.multiply(BigInteger.valueOf(i));
+            n--;
+        }
+        return result;
+    }
+
+    public static boolean[] sieve(int limit) {
+        boolean[] composite = new boolean[limit];
+        composite[0] = composite[1] = true;
+
+        int max = (int) Math.sqrt(limit);
+        for (int n = 2; n <= max; n++) {
+            if (!composite[n]) {
+                for (int k = n * n; k < limit; k += n) {
+                    composite[k] = true;
+                }
+            }
+        }
+        return composite;
+    }
+}