Try to find class resource to avoid exception

The exception thrown here when we cannot find a class can be very
expensive at boot time. For most third-party extensions, this
exception will be raised twice for every bound method, due to
double-checking the classloader under lock a second time. By first
looking for a .class resource, we can avoid the expensive
exception if it is unlikely to succeed.

core/src/main/java/org/jruby/internal/runtime/methods/InvocationMethodFactory.java

@@ -56,6 +56,7 @@
 
 import java.io.PrintWriter;
 import java.lang.reflect.Modifier;
+import java.net.URL;
 import java.util.Collections;
 import java.util.List;
 
@@ -634,11 +635,13 @@ private static void loadReceiver(String typePath, JavaMethodDescriptor desc, Ski
     private Class tryClass(String name, Class targetClass, Class expectedSuperclass) {
         final Class c;
         try {
-            if (classLoader == null) {
-                c = Class.forName(name, true, classLoader);
-            } else {
-                c = classLoader.loadClass(name);
+            URL resource = classLoader.findResource(name.replace('.', '/'));
+            if (resource == null) {
+                if (DEBUG) LOG.debug("could not find class file for " + name);
+                seenUndefinedClasses = true;
+                return null;
             }
+            c = classLoader.loadClass(name);
         } catch (ClassNotFoundException e) {
             if (DEBUG) LOG.debug(e);
             seenUndefinedClasses = true;