Question 51 :
When can an object reference be cast to an interface reference?
An object reference be cast to an interface reference when the object implements the referenced interface.
Question 52 :
What is the difference between a Window and a Frame?
The Frame class extends Window to define a main application window that can have a menu bar.
Question 53 :
Which class is extended by all other classes?
The Object class is extended by all other classes.
Question 54 :
Can an object be garbage collected while it is still reachable?
A reachable object cannot be garbage collected. Only unreachable objects may be garbage collected..
Question 55 :
Is the ternary operator written
x : y ? z or x ? y : z ?
It is written
x ? y : z