8266670: Better modeling of access flags in core reflection

Reviewed-by: mchung, rriggs, asotona

src/java.base/share/classes/java/lang/reflect/Member.java

@@ -25,6 +25,8 @@
 
 package java.lang.reflect;
 
+import java.util.Set;
+
 /**
  * Member is an interface that reflects identifying information about
  * a single member (a field or a method) or a constructor.
@@ -76,9 +78,25 @@ public interface Member {
      *
      * @return the Java language modifiers for the underlying member
      * @see Modifier
+     * @see #accessFlags()
      */
     public int getModifiers();
 
+
+    /**
+     * {@return an unmodifiable set of the {@linkplain AccessFlag
+     * access flags} for this member, possibly empty}
+     *
+     * @implSpec
+     * The default implementation throws {@link
+     * UnsupportedOperationException}.
+     * @see #getModifiers()
+     * @since 20
+     */
+    public default Set<AccessFlag> accessFlags() {
+        throw new UnsupportedOperationException();
+    }
+
     /**
      * Returns {@code true} if this member was introduced by
      * the compiler; returns {@code false} otherwise.