package org.apidesign.anagram.app.registergeneral;

 import java.util.LinkedHashMap;

 import java.util.Map;

 public final class Registry {

     private static Map<Class<?>,Object[]> instances = new LinkedHashMap<Class<?>,Object[]>();

     private Registry() {

     }

     public static void registerClass(Class<?> impl) {

         instances.put(impl, new Object[1]);

     }

     public static <T> T find(Class<T> whatType) {

         for (Map.Entry<Class<?>, Object[]> entry : instances.entrySet()) {

             if (whatType.isAssignableFrom(entry.getKey())) {

                 if (entry.getValue()[0] == null) {

                     try {

                         entry.getValue()[0] = entry.getKey().newInstance();

                     } catch (Exception ex) {

                         throw new IllegalStateException(ex);

                     }

                 }

                 return whatType.cast(entry.getValue()[0]);

             }

         }

         return null;

     }

 }