I found the following code @ https://stackoverflow.com/questions/37628/what-is-reflection-and-why-is-it-useful/37632#37632
The ability to inspect the code in the system and see object types is not reflection, but rather Type Introspection. Reflection is then the ability to make modifications at runtime by making use of introspection. The distinction is necessary here as some languages support introspection, but do not support reflection. One such example is C++.
Can anyone please elaborate on this using Java coding examples.
Thank you
Dear Zubair Jeelani
One may say introspection is anything that allows code to test what something is ("What am I?"), whereas reflection is the ability to manipulate the program structure itself.
Kind Regards
Qamar Ul Islam
Dear Qamar Ul Islam Sir
Thank you for the reply. Now to understand things better I put a scenario here.
Given a class in Java, I am using reflection API to get the methods, modifiers etc. of the same class. We call it INTROSPECTION.
Again, given a class in Java, I am using reflection API to get the methods, modifiers etc. of the different classes. We call it REFLECTION. For example, the Java disassembler, javap.
Sir, above is what I understood from your answer. If I understood you right, then a question from the comment I copied from Stackoverflow still remains and that is
Ehat does "Reflection is then the ability to make modifications at runtime by making use of introspection." this part of the comment mean.
I never made a distinction between introspection and reflection in that way. Though the way it is described in the post points out that there are two different capabilities - one is just to see the object metadata and the other is to be able to manipulate it.
One example of this is when you want to list all the properties of an object. Let's say you have a class Person and you got it from some library you have not created. if you want to know about all the properties that are exposed by this class you can either rely on documents or source code for manual check or you can use reflection (introspection as per the above definition ) to list it. Modern editors are able to show you these using IntelliSense which they implement using reflection(introspection).
A tricky example of the ability to manipulate these properties using reflection is to set the value of a private variable from outside the defining class. Though unnecessary and a bad programming practice it demonstrates capabilities of reflection in java.