JAVA FOUNDATIONS 3rd Ed By JOHN LEWIS – Test Bank

JAVA FOUNDATIONS 3rd Ed By JOHN LEWIS – Test Bank

Chapter 3: Using Classes and Objects

Multiple Choice Questions:

1)  The ________________ operator is used to instantiate an object.

a)  static

b)  new

c)  +

d)  – 

e)  none of the above

Answer: b

Explanation:  The new operator instantiates an object.  There is no static operator, and the + and – operators are for arithmetic expressions (although the + operator can also be used for String concatenation).

2)  A special method that is invoked to set up an object during instantiation is called a ___________________.

a) new method

b) dot operator 

c) creator

d) constructor

e) destructor

Answer: d

Explanation:  The constructor is called to set up an object during instantiation.  The dot operator is used to access methods of an object.  There is no “new” method – new is an operator.  Java also does not have “creators” or “destructors.”

3)  Which of the following is an invalid way to instantiate a String object?

a) String title = new String(“Java Software Solutions”);

b) String name = “John Lewis”;

c) String empty = “”;

d) String alsoEmpty = new String(“”);

e) all of the above are valid

Answer: e

Explanation:  Choices a and d represent the standard approach to instantiating a String object.  Choice d creates the empty string.  Choices b and c use a shortcut notation that is only available for creating a String object.

4)  Assume that we have a Random object referenced by a variable called a generator.  Which of the following lines will generate a random number in the range 5-20 and store it in the int variable random?

a)  randNum = generator.nextInt(15) + 5;

b)  randNum = generator.nextInt(15) + 6;

c)  randNum = generator.nextInt(16) + 5;

d)  randNum = generator.nextInt(16) + 6;

e) none of the above

Answer: c

Explanation:  When called with 16 as a parameter, the nextInt() method will return a number in the range 0 to 15.  Adding 5 to this random number will generate a number in the range 5 to 20.

5)  Which of the following classes includes the getCurrencyInstance() method?

a)  String

b)  NumberFormat

c)  DecimalFormat

d)  Math

e)  none of the above

Answer: b

Explanation:  The NumberFormat class includes the getCurrencyInstance() method.

6)  Which of the following expressions correctly computes 5 + 2⁶?

a) result = 5 + 2^6;

b) result = 5 + 2*exponent(6);

c) result = 5 + 2*Math.exponent(6);

d) result = 5 + Math.pow(2, 6);

e) none of the above

Answer: d

Explanation:  Choice a is wrong because Java does not have an exponential operator for primitive types.  Choices b and C are wrong because there are no methods named exponent in the java.lang package or the Math class.  Choice c correctly uses the Math. pow method to compute the expression.

7)  Consider the following snippet of code:

Random generator = new Random();

int randNum = generator.nextInt(20) + 1;

Which of the following will be true after these lines are executed?

a) random will hold a number between 1 and 20 inclusive.

b) random will hold a number between 0 and 20 inclusive.

c) random will hold a number between 1 and 21 inclusive.

d)  these lines will not be executed because a compiler error will result. 

e)  none of the above

Answer: a

Explanation: When called with a parameter of 20, the next () method will return an integer between 0 and 19 inclusive.  Adding one to this will result in a number between 1 and 20 inclusive.