Summary

Specify java.lang.reflect.Proxy::getInvocationHandler throws a NullPointerException instead of an IllegalArgumentException if the input argument is null.

Problem

Proxy.getInvocationHandler specifies any non-proxy-instance arguments result in an IllegalArgumentException. This does not match the actual behavior, that when null is passed, a NullPointerException is thrown.

Solution

Update the specification to match the actual behavior, which has been the case since the earliest OpenJDK history back in 2007.

Specification

diff --git a/src/java.base/share/classes/java/lang/reflect/Proxy.java b/src/java.base/share/classes/java/lang/reflect/Proxy.java
index 83a1520ce082f..1658d135cb3b4 100644
--- a/src/java.base/share/classes/java/lang/reflect/Proxy.java
+++ b/src/java.base/share/classes/java/lang/reflect/Proxy.java
@@ -967,6 +967,7 @@ public static boolean isProxyClass(Class<?> cl) {
      * @return  the invocation handler for the proxy instance
      * @throws  IllegalArgumentException if the argument is not a
      *          proxy instance
+     * @throws  NullPointerException if {@code proxy} is {@code null}
      */
     public static InvocationHandler getInvocationHandler(Object proxy)
         throws IllegalArgumentException