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  1. import java.util.Optional;
  2.  
  3. public final class Main {
  4.  
  5.     public static void main (String[] args) {
  6.         var yellow = Color.findByName("YELLOW");
  7.         yellow.ifPresent(c -> {
  8.             var rgb = c.getRgb();
  9.             System.out.println("yellow: rgb=" + rgb);
  10.         });
  11.  
  12.         // Alternatively, we may write as follows, but...
  13.         var blue = Color.findByName("BLUE");
  14.         if (blue.isPresent()) {
  15.             var rgb = blue.get().getRgb();
  16.             System.out.println("blue: rgb=" + rgb);
  17.         }
  18.     }
  19.  
  20.     public interface Color {
  21.  
  22.         /** Represents blue. */
  23.         static final Color BLUE = () -> 0xff;
  24.  
  25. 	    /**
  26. 	        Returns the Color instance that matches with the specified name.
  27.  
  28. 	        @param name
  29. 	            ...
  30. 	        @return
  31. 	            An {@link Optional<T> Optional} object containing the Color
  32. 	            instance that matches with {@code name}, or an empty Optional
  33. 	            object (if nothing matches).
  34. 	    */
  35.         static Optional<Color> findByName(String name) {
  36.             return name.equals("BLUE")
  37.                 ? Optional.of(Color.BLUE)
  38.                 : Optional.empty();
  39.         }
  40.  
  41.         /**
  42. 	        Returns the 24-bit integer value representing RGB.
  43.  
  44.             @return
  45.                 ...
  46.         */
  47.         int getRgb();
  48.     }
  49. }
  50.  
Success #stdin #stdout 0.11s 34156KB
comments (?)
stdin 
Standard input is empty
stdout 
blue: rgb=255
https://ideone.com/c99XyH
The Insanity Beyond Null: Null object pattern #6
language:
Java (HotSpot 12)
created:
4 years ago
visibility:
public

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