Update PrimeFinder.java

PrimeFinder.java

@@ -51,6 +51,7 @@ public class PrimeFinder
 
         System.out.println("Execution time: " + executionTime + " nanoseconds");
         System.out.println("Execution time: " + (executionTime / 1_000_000) + " milliseconds");
+        System.out.println("Execution time: " + (executionTime / 1_000_000_000) + " seconds");
     }
 }