Initial data commit

Task/Earliest-difference-between-prime-gaps/Java/earliest-difference-between-prime-gaps.java

@@ -0,0 +1,44 @@
+import java.util.HashMap;
+import java.util.Map;
+
+public class PrimeGaps {
+    private Map<Integer, Integer> gapStarts = new HashMap<>();
+    private int lastPrime;
+    private PrimeGenerator primeGenerator = new PrimeGenerator(1000, 500000);
+
+    public static void main(String[] args) {
+        final int limit = 100000000;
+        PrimeGaps pg = new PrimeGaps();
+        for (int pm = 10, gap1 = 2;;) {
+            int start1 = pg.findGapStart(gap1);
+            int gap2 = gap1 + 2;
+            int start2 = pg.findGapStart(gap2);
+            int diff = start2 > start1 ? start2 - start1 : start1 - start2;
+            if (diff > pm) {
+                System.out.printf(
+                    "Earliest difference > %,d between adjacent prime gap starting primes:\n"
+                    + "Gap %,d starts at %,d, gap %,d starts at %,d, difference is %,d.\n\n",
+                    pm, gap1, start1, gap2, start2, diff);
+                if (pm == limit)
+                    break;
+                pm *= 10;
+            } else {
+                gap1 = gap2;
+            }
+        }
+    }
+
+    private int findGapStart(int gap) {
+        Integer start = gapStarts.get(gap);
+        if (start != null)
+            return start;
+        for (;;) {
+            int prev = lastPrime;
+            lastPrime = primeGenerator.nextPrime();
+            int diff = lastPrime - prev;
+            gapStarts.putIfAbsent(diff, prev);
+            if (diff == gap)
+                return prev;
+        }
+    }
+}