Why multiple instances of Method object are for the inherited methods

Question

I discovered that classes with default equals method has different instances of meta object Method. Why is it so? At first glance it looks not optimal because method objects are immutable.

class X {}
Method defaultM = Object.class.getMethod("equals", Object.class)
Method xMethod =  X.class.getMethod("equals", Object.class)

xMethod != defaultM
xMethod.equals(defaultM)

Answer 1

Unfortunately, Method objects are not immutable. Since Java 2, Method extends AccessibleObject, which has the setAccessible(boolean) method.

So not only do methods have a mutable property, this flag has security impacts which disallow sharing of Method objects.

Note that under the hood, Method objects do share their common immutable state via a delegate object, so what you get from Class.getMethod is just a cheap front-end object consisting of that mutable flag and a reference to the shared canonical method representation.