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  1. import java.lang.reflect.Field;
  2. import java.lang.reflect.ParameterizedType;
  3. import java.lang.reflect.Type;
  4. import java.util.HashMap;
  5. import java.util.HashSet;
  6. import java.util.Map;
  7. import java.util.Set;
  8.  
  9. class Foo {}
  10. class Bar {}
  11. interface MyValidMap extends Map<Foo, Set<Bar>> {}
  12.  
  13. class Ideone {
  14.     public final HashMap<Foo, HashSet<Bar>> good = null;
  15.     public final Map<Foo, Set<Bar>> better = null;
  16.     public final String notAMap = null;
  17.     public final Map<String, Set<Bar>> badKey = null;
  18.     public final Map<Foo, String> badValue = null;
  19.     public final Map<Foo, Set<String>> badSetElems = null;
  20.     public final MyValidMap noTypeParamMap = null;
  21.  
  22.     public static void main(String[] args) throws Exception {
  23.         for (Field field : Ideone.class.getFields()) {
  24.             System.out.println(field.getName() + " - " + fieldMatches(field));
  25.         }
  26.     }
  27.  
  28.     private static String fieldMatches(Field mapField) throws Exception {
  29.         if (!Map.class.isAssignableFrom(mapField.getType())) {
  30.             return "Field is not a Map";
  31.         }
  32.  
  33.         if (!(mapField.getGenericType() instanceof ParameterizedType)) {
  34.             // We know it's a map, but it doesn't have type params. Probably something
  35.             // like this: class MyStringMap implements Map<String, String>. You can do
  36.             // something with getGenericInterfaces() but this seems so unlikely that
  37.             // it could just be ignored.
  38.             return "TODO";
  39.         }
  40.  
  41.         final ParameterizedType mapType = (ParameterizedType) mapField.getGenericType();
  42.         final Type keyType = mapType.getActualTypeArguments()[0];
  43.         final Type valueType = mapType.getActualTypeArguments()[1];
  44.         if (Foo.class != keyType) {
  45.             return "Map's key type is not Foo";
  46.         }
  47.  
  48.         if (!(valueType instanceof ParameterizedType)) {
  49.             // Same problem as above. May be a Set without type params
  50.             return "Map's value is (probably) not a Set";
  51.         }
  52.  
  53.         final ParameterizedType pValueType = (ParameterizedType) valueType;
  54.         final Class<?> valueClass = pValueType.getRawType() instanceof Class ?
  55.             ((Class<?>) pValueType.getRawType()) :
  56.             Ideone.class.getClassLoader().loadClass(
  57.                 pValueType.getRawType().getTypeName()
  58.             );
  59.  
  60.         if (!Set.class.isAssignableFrom(valueClass)) {
  61.             return "Map's value is not a Set";
  62.         }
  63.  
  64.         final Type setElemType = pValueType.getActualTypeArguments()[0];
  65.         if (setElemType != Bar.class) {
  66.             return "Set's elements are not Bars";
  67.         }
  68.         return "Looks good";
  69.     }
  70. }
  71.  
Success #stdin #stdout 0.1s 52996KB
comments (?)
stdin
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Standard input is empty
stdout
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good - Looks good
better - Looks good
notAMap - Field is not a Map
badKey - Map's key type is not Foo
badValue - Map's value is (probably) not a Set
badSetElems - Set's elements are not Bars
noTypeParamMap - TODO
https://ideone.com/xy4UAM
language:
Java (HotSpot 12)
created:
4 years ago
visibility:
public

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