Use computeIfAbsent instead of putIfAbsent

Author: sungshik

src/main/java/engineering/swat/watch/impl/mac/MacWatchable.java

@@ -29,18 +29,18 @@
 import static java.nio.file.StandardWatchEventKinds.OVERFLOW;
 
 import java.io.IOException;
+import java.io.UncheckedIOException;
 import java.nio.file.Path;
 import java.nio.file.WatchEvent;
 import java.nio.file.WatchKey;
 import java.nio.file.WatchService;
 import java.nio.file.Watchable;
 import java.nio.file.WatchEvent.Kind;
 import java.nio.file.WatchEvent.Modifier;
-import java.util.Arrays;
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
-
-import org.checkerframework.checker.nullness.qual.NonNull;
+import java.util.function.Function;
+import java.util.stream.Stream;
 
 public class MacWatchable implements Watchable {
     private final Path path;
@@ -67,15 +67,31 @@ public WatchKey register(WatchService watcher, Kind<?>[] events, Modifier... mod
             throw new IllegalArgumentException("A `MacWatchable` must be registered with a `MacWatchService`");
         }
 
-        // Add `OVERFLOW` to the array, as this method's documentation demands.
-        // Checker Framework: The `@NonNull` cast is only temporarily unsound.
-        events = (Kind<@NonNull ?>[]) Arrays.copyOf(events, events.length + 1);
-        events[events.length - 1] = OVERFLOW; // All elements are now `@NonNull`
+        // Add `OVERFLOW` to the array (demanded by this method's specification)
+        if (Stream.of(events).noneMatch(OVERFLOW::equals)) {
+            events = Stream
+                .concat(Stream.of(events), Stream.of(OVERFLOW))
+                .toArray(Kind<?>[]::new);
+        }
+
+        // Wrap any `IOException` thrown by the constructor of `MacWatchKey` in
+        // an `UncheckedIOException`. Intended to be used when invoking
+        // `computeIfAbsent`.
+        Function<MacWatchService, MacWatchKey> newMacWatchKey = service -> {
+            try {
+                return new MacWatchKey(this, service);
+            } catch (IOException e) {
+                throw new UncheckedIOException(e);
+            }
+        };
 
-        var service = (MacWatchService) watcher;
-        var newKey = new MacWatchKey(this, service);
-        var oldKey = registrations.putIfAbsent(service, newKey);
-        return (oldKey != null ? oldKey : newKey).initialize(events, modifiers);
+        try {
+            return registrations
+                .computeIfAbsent((MacWatchService) watcher, newMacWatchKey)
+                .initialize(events, modifiers);
+        } catch (UncheckedIOException e) {
+            throw e.getCause();
+        }
     }
 
     @Override