Chapter 9 Review

bowtietigers
Quiz by bowtietigers, updated more than 1 year ago
bowtietigers
Created by bowtietigers over 5 years ago
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Description

Review for chapter 9, which is on interfaces.

Resource summary

Question 1

Question
Which of the following choices might serve as an interface for the other choices listed?
Answer
  • Piano
  • Drum
  • Guitar
  • Instrument
  • FrenchHorn

Question 2

Question
Which of the following code segments causes a compile-time error?
Answer
  • Airplane boeing707 = new Airplane();
  • Flier boeing707 = new Flier();
  • Flier boeing707 = new Airplane();
  • Airplane boeing707 = new Airplane(); Flier airTraveler = boeing707;
  • Airplane boeing707 = new Airplane(); Flier airTraveler; airTraveler = (Airplane) beoing707;

Question 3

Question
Consider the following code segment. 1 Airplane skyRider = new Airplane(); 2 Flier skyRider2 = skyRider; 3 Athlete skyRider3 = (Athlete) skyRider2; 4 Airplane skyRider4 = (Airplane) skyRider2; 5 Flier skyRider5 = skyRider4; Which statement above will cause a run-time error and throw an exception?
Answer
  • Statement 1
  • Statement 2
  • Statement 3
  • Statement 4
  • Statement 5

Question 4

Question
Airplane c = new Airplane(); Flier f = new Airplane(); Athlete a = new SkiJumper("Ann", "Smith"); SkiJumper s = new SkiJumper("John", "Doe"); Which of the following statements is not legal?
Answer
  • c.fly();
  • f.fly();
  • a.train(3);
  • s.train(3);
  • a.fly();

Question 5

Question
Airplane c = new Airplane(); Flier f = new Airplane(); Athlete a = new SkiJumper("Ann", "Smith"); SkiJumper s = new SkiJumper("John", "Doe"); Which of the following statements needs a cast? I. f = c; II. a = s; III. s = a;
Answer
  • I only
  • II only
  • III only
  • I and II only
  • I and III only

Question 6

Question
Suppose class C implements an interface I by implementing all of the methods of I and no further methods. Then which of the following must be true?
Answer
  • All instance variables or C are public.
  • All methods of C are abstract.
  • All methods of C are public.
  • All constants of C are public.
  • All instance variables of C are private.

Question 7

Question
Which of the following statements is true about casting?
Answer
  • You must cast to convert from an interface type to a class type.
  • You must cast to convert from a class type to an interface type.
  • You cannot cast to convert an interface type to a class type.
  • You cannot cast from a class type to an interface type.
  • Both a and b above are true.

Question 8

Question
Which of the following statements is true about dynamic binding?
Answer
  • Dynamic binding occurs during compile time.
  • Dynamic binding occurs when the appropriate overloaded method is selected.
  • Dynamic binding is another name for early binding.
  • In dynamic binding, the virtual machine selects the appropriate method.
  • Dynamic binding occurs only when an interface declares public static final constants.

Question 9

Question
Which of the following statements about interfaces is not true?
Answer
  • An interface can specify constants that can be used by all classes that implement the interface.
  • An interface can specify variables that can be used by all classes that implement the interface.
  • An interface can specify methods that must be defined by all classes that implement the interface.
  • An interface name cannot be instantiated.
  • The interface contains declarations but not implementations.

Question 10

Question
Suppose foo is an object of class C, and C implements the interface type I. Which of the following statements must be true?
Answer
  • foo was constructed with the constructor of I.
  • C assigns values to all constants declared in the interface I.
  • C supplies an implementation for all methods of the interface I.
  • foo must be declared as I foo = new C();
  • All methods of I are declared as private.
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