Exam 1

Question 1

Abstraction

Answer 1

Provide high-level model of activity or data

Don’t worry about the details; What does it do, not how

Question 2

Procedural Abstraction

Answer 2

Specify what actions should be performed

Hide algorithms

Question 3

Data Abstraction

Answer 3

Specify data objects for problem

Hide Representation

Question 4

Abstract Data Type (ADT)

Answer 4

Implementation independent of interfaces

Question 5

Encapsulation

Answer 5

A design technique that calls for hiding implementation details while providing an interface (methods) for data access

Allows us to code without having to know its implementation
Change the internals all you want, but just keep the interface constant

Question 6

Interfaces

Answer 6

Allows us to express an ADT
Provides abstract methods
Defines an IS-A relationship

Question 7

Class

Answer 7

Blueprint for an object

Question 8

a.compareTo(b) returns?

Answer 8

Negative if a < b
0 if a == b
Positive if a > b

Question 9

Inheritance

Answer 9

The process by which one new class, called the derived class (subclass/child class), is created from another class, called the base class (superclass/parent class)

Question 10

extends

Answer 10

Specifies that a class is a derived class of another class

Question 11

super()

Answer 11

refers to the parent class object
calls the constructor of the parent class
Must be the first line in the child class' constructor

Question 12

Overriding

Answer 12

A derived class redefines existing methods of the parent class

Question 13

Overloading

Answer 13

When two or more methods have the same name but different parameters

Question 14

this

Answer 14

refers to the current object

Question 15

Protected

Answer 15

a class element that is only accessible to any derived class or any class in the same package

Question 16

Early (static) binding

Answer 16

method that is called depends on the declared type of the referring variable, and not the object’s actual type

Question 17

Late (dynamic) binding

Answer 17

method that is called depends on an object’s actual type, and not the declared type of the referring variable

Question 18

Does java use early or late binding

Answer 18

Late binding

Question 19

Polymorphism

Answer 19

When a single reference variable refers to objects of many different types

Question 20

Upcasting

Answer 20

Casting a reference to a parent class
This is done automatically and is always safe

Question 21

Downcasting

Answer 21

casting a reference to a child class
May not be legal depending on the actual object type
You can force it by performing an explicit cast

Question 22

What does a ClassCastException mean?

Answer 22

Illegal downcasting occurred

Question 23

what is the stack

Answer 23

makes possible method execution

makes recursion possible

Question 24

what is the heap

Answer 24

where objects are created

Question 25

Recursion

Answer 25

A procedure that calls itself

Relies on the call stack

Question 26

Abstract methods

Answer 26

Give a signature but no body

Class descendants provide the implementation

Question 27

Abstract class

Answer 27

required if class contains any abstract method

Question 28

Program Correctness

Answer 28

determined by the presence/absence of program defects (errors/bugs)

Question 29

Types of program errors

Answer 29

Compile-time
Run-time
Logic

Question 30

Compile-Time errors

Answer 30

Detected during compilation

Lexical, grammatical, type errors

Question 31

Run-time errors

Answer 31

Detected during program execution

Operations are illegal/impossible to run

Question 32

Logical errors

Answer 32

Operation leading to incorrect program state

Problem in design or implementation of algorithm

Question 33

Reference copy

Answer 33

Makes copy of reference

x = y

Question 34

Shallow Copy

Answer 34

Makes copy of object

x = y.clone();

Question 35

Deep Copy

Answer 35

Makes copy of object and all objects directly or indirectly referred to by the object

Question 36

Cloning

Answer 36

We can create a copy of an object using the clone() method
Object class provides a clone() method that provides shallow copying

Question 37

Initialization Block

Answer 37

Block of code used to initialize static and instance variables for class

Question 38

Static Initialization Block

Answer 38

Executed only once
Code executed before class is used