Move findLoadedClass to inside the lock

Fixes #10031

independent-projects/bootstrap/runner/src/main/java/io/quarkus/bootstrap/runner/RunnerClassLoader.java

@@ -15,7 +15,6 @@
 
 /**
  * Classloader used for production application, using the multi jar strategy
- *
  */
 public class RunnerClassLoader extends ClassLoader {
 
@@ -33,7 +32,7 @@ public class RunnerClassLoader extends ClassLoader {
     }
 
     RunnerClassLoader(ClassLoader parent, Map<String, ClassLoadingResource[]> resourceDirectoryMap,
-            Set<String> parentFirstPackages) {
+                      Set<String> parentFirstPackages) {
         super(parent);
         this.resourceDirectoryMap = resourceDirectoryMap;
         this.parentFirstPackages = parentFirstPackages;
@@ -49,10 +48,6 @@ public Class<?> loadClass(String name, boolean resolve) throws ClassNotFoundExce
         //note that for performance reasons this CL does not do parent first delegation
         //although the intention is not for it to be a true isolated parent first CL
         //'delegation misses' where the parent throws a ClassNotFoundException are very expensive
-        Class<?> loaded = findLoadedClass(name);
-        if (loaded != null) {
-            return loaded;
-        }
         if (name.startsWith("java.")) {
             return getParent().loadClass(name);
         }
@@ -61,6 +56,10 @@ public Class<?> loadClass(String name, boolean resolve) throws ClassNotFoundExce
             return getParent().loadClass(name);
         }
         synchronized (getClassLoadingLock(name)) {
+            Class<?> loaded = findLoadedClass(name);
+            if (loaded != null) {
+                return loaded;
+            }
             ClassLoadingResource[] resources;
             if (packageName == null) {
                 resources = resourceDirectoryMap.get("");