Factorial primes: Difference between revisions

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 (i.28x here would have given us an eleventh prime, but the task asked for the first 10, and the stretch goal requires considerable patience.)
+=={{header|Java}}==
+<syntaxhighlight lang="java">
+public class MainApp {
+    public static void main(String[] args) {
+        int countOfPrimes = 0;
+        final int targetCountOfPrimes = 10;
+        long f = 1;
+        while (countOfPrimes < targetCountOfPrimes) {
+            long factorialNum = getFactorial(f);
+            boolean primePlus = isPrime(factorialNum + 1);
+            boolean primeMinus = isPrime(factorialNum - 1);
+            if (primeMinus) {
+                countOfPrimes++;
+                System.out.println(countOfPrimes + ": " + factorialNum + "! - 1 = " + (factorialNum - 1));
+            }
+            if (primePlus  && f > 1) {
+                countOfPrimes++;
+                System.out.println(countOfPrimes + ": " + factorialNum + "! + 1 = " + (factorialNum + 1));
+            }
+            f++;
+        }
+    }
+    private static long getFactorial(long f) {
+        long factorial = 1;
+        for (long i = 1; i < f; i++) {
+            factorial *= i;
+        }
+        return factorial;
+    }
+    private static boolean isPrime(long num) {
+        if (num < 2) {return false;}
+        for (long i = 2; i < num; i++) {
+            if (num % i == 0) {return false;}
+        }
+        return true;
+    }
+}
+</syntaxhighlight>
+Results
+<pre>
+: 1! + 1 = 2
+: 2! + 1 = 3
+: 6! - 1 = 5
+: 6! + 1 = 7
+: 24! - 1 = 23
+: 720! - 1 = 719
+: 5040! - 1 = 5039
+: 39916800! + 1 = 39916801
+: 479001600! - 1 = 479001599
+: 87178291200! - 1 = 87178291199
+</pre>
 =={{header|jq}}==