Reflection

Question 1

What is the purpose of Java Reflection?

Answer 1

To enable programs to analyse themselves as well as other programs. Specifically, analysing fields, constructors
and methods of all accessors.

Question 2

What is the entry point for the Reflection API?

Answer 2

The entry point of reflection is an immutable instance of the objects .class.

Question 3

Why is Reflection costly?

Answer 3

Because it uses dynamic type checking as well as requires run time permissions.

Question 4

Reflections breaks Java conventions. What might this result in?

Answer 4

Unexpected and unreliable output.

Question 5

What are the 3 ways to obtain the class entry point for reflection?

Answer 5

• getInstace() called on the object.
• Access from the type E.g. float.class (works on reference and primitive types).
• forName() to get the class of the specified name.

Question 6

What’s the difference between getFields() and getDeclaredFields()?

Answer 6

getFields() returns all public fields, including inherited ones.
getDeclaredFields() returns all fields (including private). Doesn’t include inherited fields.

Question 7

What are the 2 main methods of creating new object instances in Reflection?

Answer 7

Constructor.newInstance() is used to call constructor of any accessor and argument type.
Class.newInstance() is used if constructor has no arguments and is public.

Question 8

How can we modify private members using Reflection?

Answer 8

We have to temporarily modify the accessor of the member via setAccessible(true), and then we can
change the value. This is done in a try catch.

Question 9

What are the 3 main uses of Reflection?

Answer 9

Force specific program states for testing.
Ensure a high level of code coverage.
Enable inspection of running programs for bugs.