introduce bitloops

src/main/java/puzzle/Main.java

@@ -125,6 +125,7 @@ public class Main {
          else rebuildIndex();
          info("indexUpdated : " + INDEX_FILE);
       } catch (IOException e) {
+         e.printStackTrace();
          err("Failed to write: " + FILE_NAME);
          err("Reason       : " + e.getMessage());
          System.exit(2);
@@ -344,6 +345,15 @@ public class Main {
    }
    
    static PuzzleResult attempt(Rng rng, Dict dict, Opts opts) {
+      try {
+        return  _attempt(rng, dict, opts);
+      } catch (Exception e) {
+         e.printStackTrace();
+         System.err.println("Failed to operate" + e.getMessage());
+         return null;
+      }
+   }
+   static PuzzleResult _attempt(Rng rng, Dict dict, Opts opts) {
       TOTAL_ATTEMPTS.incrementAndGet();
       var swe    = new SwedishGenerator(rng);
       var mask   = swe.generateMask(opts.pop, opts.gens, Math.max(opts.pop, (int) Math.floor(opts.pop * 1.5)));
@@ -422,6 +432,7 @@ public class Main {
          Files.writeString(indexPath, content, StandardCharsets.UTF_8);
          info("indexUpdated : " + indexPath);
       } catch (IOException e) {
+         e.printStackTrace();
          err("Failed to update index.json: " + e.getMessage());
       }
    }
@@ -462,10 +473,12 @@ public class Main {
                      var pathInIndex = "/puzzles/" + filename;
                      records.add(toIndexRecordJson(id, pathInIndex, date, theme, difficulty, createdAt));
                   } catch (IOException e) {
+                     e.printStackTrace();
                      err("Failed to read " + path + ": " + e.getMessage());
                   }
                });
       } catch (IOException e) {
+         e.printStackTrace();
          err("Failed to list puzzles: " + e.getMessage());
          return;
       }
@@ -476,6 +489,7 @@ public class Main {
          Files.writeString(indexPath, content, StandardCharsets.UTF_8);
          info("Successfully rebuilt index.json with " + records.size() + " records.");
       } catch (IOException e) {
+         e.printStackTrace();
          err("Failed to write index.json: " + e.getMessage());
       }
    }