Quiz Bank For Java Foundations Third Edition By John Lewis
ISBN-10:0133370461 , ISBN-13:978-0133370461
Chapter 3: Utilizing Lessons and Objects
Several Questions of Selection:
1) The ________________ operator serves the purpose of creating an object.
a) static
b) new
c) +
d) –
e) none of the above
Answer: b
Explanation: The new operator is utilized for object creation. There is no static operator, and the + and – operators are for arithmetic operations (although the + operator can also be used for String concatenation).
2) A specific method invoked to initialize an object during instantiation is known as a ___________________.
a) new method
b) dot operator
c) creator
d) constructor
e) destructor
Answer: d
Explanation: The constructor is responsible for initializing an object during instantiation. The dot operator is used to access object methods. There is no “new” method – new is an operator. Java also does not have “creators” or “destructors”.
3) Which of the following is an incorrect way to create 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 correct
Answer: e
Explanation: Choices a and d depict the standard way of instantiating a String object. Choice d creates the empty string. Choices b and c use a shortcut notation specific to creating a String object.
4) Assume that we have a Random object referenced by a variable named generator. Which of the following lines will generate a random number in the range 5-20 and assign it to the integer variable randNum?
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 the nextInt() method is called with 16 as a parameter, it 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 contain 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 compute 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 incorrect as Java does not have an exponential operator for primitive types. Choices b and C are incorrect as 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 code snippet:
Random generator = new Random();
int randNum = generator.nextInt(20) + 1;
Which of the following statements is true after executing these lines?
a) randNum will hold a number between 1 and 20 inclusive.
b) randNum will hold a number between 0 and 20 inclusive.
c) randNum will hold a number between 1 and 21 inclusive.
d) these lines will not be executed due to a compiler error.
e) none of the above
Answer: a
Explanation: When nextInt() is called with a parameter of 20, it will return an integer between 0 and 19 inclusive. Adding one to this will result in a number between 1 and 20 inclusive.
8) Which of the following represents the correct way to create a NumberFormat object that formats numbers as percentages?
a) NumberFormat fmt = new NumberFormat(%);
b) NumberFormat fmt = new NumberFormat(“%”);
c) NumberFormat fmt = NumberFormat.getPercentInstance();
d) NumberFormat fmt = new PercentNumberFormat();
e) none of the above
Answer: c
Explanation: The NumberFormat class uses factory methods to construct objects. The new operator is implicitly called in this case. The factory method used here is getPercentInstance(). Therefore option c is correct. Options a and b are incorrect as they explicitly call the new operator. Option d is incorrect as there is no PercentNumberFormat class that can be called with the new constructor.
9) Which of the following is a valid declaration of an enumerated type for the suits of a deck of cards?
a) enumerated type Suit = { hearts, spades, diamonds, clubs };
b) enum Suit {hearts, spades, diamonds, clubs };
c) enum Suit {hearts, spades, diamonds, clubs }
d) enumerated type Suit = {hearts, spades, diamonds, clubs };
e) enum Suit = { hearts, spades, diamonds, clubs }
Answer: c
Explanation: Option c represents the correct syntax for declaring an enumerated type named Suit that can take one of the values hearts, spades, diamonds, or clubs.
10) ____________________ is the automatic conversion between a primitive value and a corresponding wrapper object.
a) Generating
b) Aliasing
c) Number formatting
d) Static invocation
e) Autoboxing
Answer: e
Explanation: Autoboxing facilitates the automatic conversion between a primitive value and a corresponding wrapper object. The other four answers are incorrect.
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