--- old/src/java.instrument/share/classes/java/lang/instrument/Instrumentation.java	2020-04-12 17:30:06.000000000 -0700
+++ new/src/java.instrument/share/classes/java/lang/instrument/Instrumentation.java	2020-04-12 17:30:06.000000000 -0700
@@ -395,12 +395,30 @@
     getAllLoadedClasses();
 
     /**
-     * Returns an array of all classes for which <code>loader</code> is an initiating loader.
-     * If the supplied loader is <code>null</code>, classes initiated by the bootstrap class
-     * loader are returned.
+     * Returns an array of all classes which {@code loader} can find by name
+     * via {@link ClassLoader#loadClass(String, boolean) ClassLoader::loadClass},
+     * {@link Class#forName(String) Class::forName} and bytecode linkage.
+     * That is, {@code loader} has been recorded as an initiating loader
+     * of these classes. If the supplied {@code loader} is {@code null},
+     * classes that the bootstrap class loader can find by name are returned.
+     *
+     * <p>
+     * The returned array does not include {@link Class#isHidden()
+     * <em>hidden</em>} classes or interfaces that are created by the invocation of
+     * {@link java.lang.invoke.MethodHandles.Lookup#defineHiddenClass(byte[], boolean, java.lang.invoke.MethodHandles.Lookup.ClassOption...)
+     * Lookup::defineHiddenClass} because:
+     * <ul>
+     * <li>A hidden class or interface cannot be referenced by the constant pools
+     *     of other classes and interfaces.
+     * <li>A hidden class or interface cannot be discovered by any class loader.
+     * </ul>
+     * In addition, the returned array does not include array classes whose
+     * {@linkplain Class#componentType() element type} is a
+     * {@link Class#isHidden() hidden class or interface} as they cannot
+     * be discovered by {@code loader}.
      *
      * @param loader          the loader whose initiated class list will be returned
-     * @return an array containing all the classes for which loader is an initiating loader,
+     * @return an array containing all classes which {@code loader} can find by name;
      *          zero-length if there are none
      */
     @SuppressWarnings("rawtypes")