Replace switch with reflection in generated code

This patch expands on the suggestion in
ben-manes#110 (comment)

Instead of the proposed numeric code the name of factory is used as the
classname to instantiate using reflection.
This reduces the class size with 21K bringing the jar size to 786K.

caffeine/src/javaPoet/java/com/github/benmanes/caffeine/cache/LocalCacheSelectorCode.java

@@ -15,6 +15,7 @@
  */
 package com.github.benmanes.caffeine.cache;
 
+import java.lang.reflect.Constructor;
 import java.util.Set;
 
 import com.squareup.javapoet.CodeBlock;
@@ -88,16 +89,18 @@ private LocalCacheSelectorCode expires() {
     return this;
   }
 
-  private LocalCacheSelectorCode selector(Set<String> classNames) {
-    CodeBlock.Builder switchBuilder = CodeBlock.builder();
-    switchBuilder.beginControlFlow("switch (sb.toString())");
-    for (String className : classNames) {
-      switchBuilder.addStatement(
-          "case $S: return new $N<>(builder, cacheLoader, async)", className, className);
-    }
-    switchBuilder.addStatement("default: throw new $T(sb.toString())", IllegalStateException.class);
-    switchBuilder.endControlFlow();
-    block.add(switchBuilder.build());
+  private LocalCacheSelectorCode selector() {
+    CodeBlock.Builder reflectBuilder = CodeBlock.builder();
+    reflectBuilder.add("try {\n"
+            + "  Class<?> cls = LocalCacheFactory.class.getClassLoader()\n"
+            + "    .loadClass(\"com.github.benmanes.caffeine.cache.LocalCacheFactory$$\" + sb.toString());\n"
+            + "  $T<?> ctor = cls.getDeclaredConstructor(Caffeine.class, CacheLoader.class, boolean.class);\n"
+            + "  return (BoundedLocalCache<K, V>) ctor.newInstance(builder, cacheLoader, async);\n"
+            + "} catch (ReflectiveOperationException e) {\n"
+            + "  throw new IllegalStateException(sb.toString());\n"
+            + "}\n"
+            + "\n", Constructor.class);
+    block.add(reflectBuilder.build());
     return this;
   }
 
@@ -113,7 +116,7 @@ public static CodeBlock get(Set<String> classNames) {
         .stats()
         .maximum()
         .expires()
-        .selector(classNames)
+        .selector()
         .build();
   }
 }