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  1. import java.lang.annotation.ElementType;
  2. import java.lang.annotation.Retention;
  3. import java.lang.annotation.RetentionPolicy;
  4. import java.lang.annotation.Target;
  5. import java.lang.reflect.Field;
  6.  
  7. // The @UserPreference annotation:
  8. @Retention(RetentionPolicy.RUNTIME)
  9. @Target(ElementType.FIELD)
  10. @interface UserPreference {
  11. }
  12.  
  13. // Example class has 4 fields, 3 are tagged with @UserPreference:
  14. class Example {
  15.     @UserPreference String description;
  16.     @UserPreference int quantity;
  17.     @UserPreference double weight;
  18.     String secret;
  19.     Example () {
  20.         description = "Tribble";
  21.         quantity = 10000;
  22.         weight = 0.48;
  23.         secret = "Note: Trouble";
  24.     }
  25. }
  26.  
  27. public class Main {
  28.  
  29.     static void printPreferences (Object o) {
  30.         for (Field f : o.getClass().getDeclaredFields()) {
  31.             if (f.getAnnotation(UserPreference.class) != null) {
  32.                 try {
  33.                     String name = f.getName();
  34.                     Object val = f.get(o);
  35.                     System.out.println(name + "=" + val);
  36.                 } catch (IllegalAccessException x) {
  37.                     System.err.println("Skipping inaccessible field: " + x);
  38.                 }
  39.             }
  40.         }
  41.     }
  42.  
  43.     public static void main(String[] args) {
  44.         printPreferences(new Example());
  45.     }
  46.  
  47. }
  48.  
Success #stdin #stdout 0.1s 380352KB
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Standard input is empty
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description=Tribble
quantity=10000
weight=0.48
https://ideone.com/PEojDE
language:
Java (HotSpot 12)
created:
10 years ago
visibility:
public

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