2: Quizzes

Question 1

Which of the following is NOT a Java relational operator?

=
>=
!=
>

Answer 1

=

Question 2

Which of the following is true?

1. When using == to compare reference variables, you are testing for “identity equality” – that the two variables refer to the same object.
2. The .equals() method tests for “content equality” – that the objects are considered equivalent to each other.

Answer 2

1 and 2 are both true.

Question 3

Which of the following operators may NOT be used with operands of type boolean?

&&
||
!=
!

Answer 3

All of these may be used with type boolean.

Question 4

What is a common use for a variable of type boolean?

Answer 4

Flag variable

Question 5

What is a common name for a method that returns type boolean?

Answer 5

Predicate method

Question 6

What are the valid data types for a switch statement.

Answer 6

int, char, String

Question 7

If a break statement is not included at the end of each action (alternative) in a switch instruction, what is the result?

Answer 7

More than one action may be executed.

Question 8

You are writing a program that will allow a user to enter a single word identifying her ‘sign’ in the Chinese zodiac (e.g. “Dog”) and then show some information about that sign. Obviously a decision must be made in this program. Which selection structure(s) could you use that will compile?

Answer 8

Either if statements or a switch statement could be used.

Question 9

Which of the following is true in Java?

1. Every else must have a preceding if.
2. Every if must have a following else.

Answer 9

1 is true.

Question 10

What kind of loop is a data validation loop?

Answer 10

An indefinite loop.

Question 11

Which loop control structure can NOT be used if there are conditions under which the body of the loop should be executed zero times?

Answer 11

do…while

Question 12

You know that a for loop is usually the best choice for a counting loop, but which other loop control structure(s) could possibly be used to create a counting loop?

Answer 12

Any of the loop control structures can be used to create a counting loop.

Question 13

How are the following implemented?

1. The state of an object.
2. The behavior of an object.

Answer 13

1. Through instance variables.

2. Through instance methods.

Question 14

Another term for instance variable is…?

Answer 14

Field.

Question 15

What is the keyword for the implicit parameter?

Answer 15

this

Question 16

A method that changes the state of an object is known as….

Answer 16

a mutator.

Question 17

A method that provides information about the state of an object is known as…

Answer 17

an accessor.

Question 18

A piece of code that initializes the state of an object is known as…

Answer 18

a constructor.

Question 19

What is the keyword used to encapsulate the fields of an object?

Answer 19

private

Question 20

An object’s properties are also known as what?

Answer 20

Instance variables

Question 21

What is another name for an object?

Answer 21

An instance of a class.

Question 22

Which of the following statements is FALSE?

1. A private method may be called from anywhere within the class in which it is declared.
2. A public attribute may be examined from anywhere in the program, but may not be changed.
3. The keyword void indicates that a method does not return any value.

Answer 22

2 is false.

Question 23

Which of the following things does this statement do?

Color darkBrown = new Color( 120, 160, 0 );

1. Declare a new variable.
2. Construct a new object.
3. Create a binding.
4. All of the above.
5. None of the above.

Answer 23

4. All of the above.

Question 24

An object diagram represents what?

Answer 24

The state of memory at a particular point during the execution of a program.

Question 25

When drawing an object diagram, you evaluate a series of program statements to figure out how they change the contents of memory. Which of the following is a question you should ask as you evaluate each line of code?

1. Does the line of code declare a variable?
2. Does the line of code instantiate an object?
3. Does the line of code create a binding?
4. All of the above.
5. None of the above.

Answer 25

4. All of the above.

Question 26

Which of the following valid statements declares a variable? 
/* 1 */ Oval dot = new Oval(); 
/* 2 */ dot.setColor( new Color( 0, 0, 255 ) ); 
/* 3 */ dot.setFilled(); 
/* 4 */ Oval circle; 
/* 5 */ circle = dot;

Answer 26

1 & 4.

Question 27

Which of the following valid statements creates (constructs) an object? [Read very carefully!] 
/* 1 */ Oval dot = new Oval(); 
/* 2 */ dot.setColor( new Color( 0, 0, 255 ) ); 
/* 3 */ dot.setFilled(); 
/* 4 */ Oval circle; 
/* 5 */ circle = dot;

Answer 27

1 & 2

Question 28

Which of the following valid statements creates a binding (assigns a value to a variable)? 
/* 1 */ Oval dot = new Oval(); 
/* 2 */ dot.setColor( new Color( 0, 0, 255 ) ); 
/* 3 */ dot.setFilled(); 
/* 4 */ Oval circle; 
/* 5 */ circle = dot;

Answer 28

1 & 5.

Question 29

Which of the following valid statements creates an alias? 
/* 1 */ Oval dot = new Oval(); 
/* 2 */ dot.setColor( new Color( 0, 0, 255 ) ); 
/* 3 */ dot.setFilled(); 
/* 4 */ Oval circle; 
/* 5 */ circle = dot;

Answer 29

5

Question 30

What is an orphaned object?

Answer 30

An object which has no references to it.

Question 31

What are the different views of a class?

1. Source code
2. UML Class Diagram
3. Javadoc comments

Answer 31

1, 2 and 3.

Question 32

What does the keyword ‘this’ refer to when used in a statement in code?

Answer 32

The particular object executing the statement.

Question 33

Name two access modifiers.

Answer 33

public and private.

Question 34

What is the proper JavaDoc tag for parameter descriptions?

Answer 34

@param

Question 35

Javadoc comments are for client programmers. True/False

Answer 35

True

Question 36

What is the name of the package needed to use File objects.

Answer 36

java.io

Question 37

What is the throws clause that we include in our method signature when the method instantiates a Scanner to read from a File?

Answer 37

throws FileNotFoundException

Question 38

The proper syntax to create a Scanner object that can read from the text file words.txt is

Scanner sc = new Scanner(“file.txt”);

Answer 38

False

Question 39

How many steps are required to successfully swap the values in two variables?

Answer 39

3

Question 40

Given the following declaration:
double[][] y = {{ 1, 2, 3, -1}, {4, 5, 6, 0}, {7, 8, 9, 10}};

What is the proper syntax to access the -1?

Answer 40

y[0][3]

Question 41

In order to visit every element in a 2-dimensional array, what control structure design do you need?

Answer 41

A loop nested within another loop

Question 42

Which sort algorithm begins with the algorithm below?
start at index 1
copy array value into temporary storage
compare temporary to index 0 - if element 0 is less than element 1,
shift element 0 to element 1
put temporary value into element 0

Answer 42

Insertion sort

Question 43

Given a 2-dimensional array of ints, what will the following code do?

int sum = 0;
for (int r = 0; r < array.length; r++) {
for ( c= 0; c < array[r].length; c++)
sum += array[r][c];
}
System.out.println(sum);

Answer 43

Prints out the sum of the entire array

Question 44

Given a 2-dimensional array of ints, what will the following code do?

int sum = 0;
for (int r = 0; r < array.length; r++, sum = 0) {
for ( c= 0; c < array[r].length; c++)
sum += array[r][c];
System.out.println(sum);
}

Answer 44

Prints the sum of each row

Question 45

Which sort algorithm is described below?
set top of unsorted array to 0
search array from top to end to find index of largest entry
swap value at top of array with value at index of largest entry
increment top
repeat until end of loop

Answer 45

Selection sort

Question 46

You can swap 2 rows of a 2-dimensional array (true/false)

Answer 46

True

Question 47

Inheritance represents what type of relationship?

Answer 47

Is-a relationship

Question 48

What is the keyword used to indicate a class inheritance relationship?

Answer 48

extends

Question 49

A sub class may not access any private members of the super class by name. (true/false)

Answer 49

True

Question 50

What is the keyword used by a sub class to call a super class constructor?

Answer 50

super

Question 51

When we implement the method: String toString() {} in our classes, we are ______ the method from the Object class.

Answer 51

overriding