Summary

Problem

MethodHandleProxies.asInterfaceInstance does not support default methods and does not mention such methods with regards to selection of the uniquely named method.

Solution

Refer to default methods with regards to selection of the uniquely named method.

Specification

diff -r 61f5673d6d02 src/java.base/share/classes/java/lang/invoke/MethodHandleProxies.java
--- a/src/java.base/share/classes/java/lang/invoke/MethodHandleProxies.java     Tue Jul 10 12:22:07 2018 -0700
+++ b/src/java.base/share/classes/java/lang/invoke/MethodHandleProxies.java     Wed Jul 11 11:05:36 2018 -0700
@@ -52,8 +54,10 @@
      * A single-method interface is an interface which declares a uniquely named method.
      * When determining the uniquely named method of a single-method interface,
      * the public {@code Object} methods ({@code toString}, {@code equals}, {@code hashCode})
-     * are disregarded.  For example, {@link java.util.Comparator} is a single-method interface,
-     * even though it re-declares the {@code Object.equals} method.
+     * are disregarded as are any default (non-abstract) methods.
+     * For example, {@link java.util.Comparator} is a single-method interface,
+     * even though it re-declares the {@code Object.equals} method and also
+     * declares default methods, such as {@code Comparator.reverse}.
      * <p>
      * The interface must be public.  No additional access checks are performed.
      * <p>