Intro to Classes, Objects, Methods and Strings

Question 1

a) A ___ method is a special method that you can call without first creating an object of the class in which it is declared.

Answer 1

a) static

Question 2

b) Keyword \_\_\_ in a class declaration is 
followed immediately by the class’s name.

Answer 2

b) class

Question 3

c) Keyword ___ requests memory from the system to store an object, then calls the
corresponding class’s constructor to initialize the object.

Answer 3

c) new

Question 4

d) Each parameter must specify both a(n) ___ and a(n) ___ .

Answer 4

d) type, name

Question 5

e) By default, classes that are compiled in the same directory are considered to be in the
same package, known as the ___ .

Answer 5

e) default package

Question 6

f) When each object of a class maintains its own copy of an attribute, the field that represents the attribute is also known as a(n) ___ .

Answer 6

f) instance variable

Question 7

g) Java provides two primitive types for storing floating-point numbers in memory: ___ and ___ .

Answer 7

g) float, double

Question 8

h) Variables of type double represent ___ floating-point numbers.

Answer 8

h) double-precision

Question 9

i) Scanner method ___ returns a double value.

Answer 9

i) nextDouble

Question 10

j) Keyword public is an access ___ .

Answer 10

j) modifier

Question 11

k) Return type ___ indicates that a method will not return a value.

Answer 11

k) void

Question 12

l) Scanner method ___ reads characters until it encounters a newline character, then returns those characters as a String.

Answer 12

l) nextLine

Question 13

m) Class String is in package ___ .

Answer 13

m) java.lang

Question 14

n) A(n) ___ is not required if you always refer to a class with its fully qualified class name.

Answer 14

n) import declaration

Question 15

o) A(n) ___ is a number with a decimal point , such as 7.33, 0.0975 or 1000.12345.

Answer 15

o) floating-point number

Question 16

p) Variables of type float represent ___ floating-point numbers.

Answer 16

p) single-precision

Question 17

q) The format specifier ___ is used to output values of type float or double.

Answer 17

q) %f

Question 18

r) Types in Java are divided into two categories— ___ types and ___ types.

Answer 18

r) primitive, reference

Question 19

a) By convention, method names begin with an uppercase first letter, and all subsequent
words in the name begin with a capital first letter.

Answer 19

a) False. By convention, method names begin with a lowercase first letter and all subsequent words in the name begin with a capital first letter

Question 20

b) An import declaration is not required when one class in a package uses another in the same package.

Answer 20

b) True

Question 21

c) Empty parentheses following a method name in a method declaration indicate that the method does not require any parameters to perform its task.

Answer 21

c) True

Question 22

d) Variables or methods declared with access modifier private are accessible only to methods of the class in which they’re declared.

Answer 22

d) True

Question 23

e) A primitive-type variable can be used to invoke a method.

Answer 23

e) False. A primitive-type variable cannot be used to invoke a method—a reference to an object is required to invoke the object’s methods.

Question 24

f) The compiler provides a default constructor with no parameters in any class that does
not explicitly include a constructor.

Answer 24

f) True

Question 25

g) Every method’s body is delimited by left and right braces ({ and }).

Answer 25

g) True

Question 26

h) Primitive-type local variables are initialized by default.

Answer 26

h) False. Primitive-type instance variables are initialized by default. Each local variable must explicitly be assigned a value

Question 27

i) Reference-type instance variables are initialized by default to the value null.

Answer 27

i) True

Question 28

j) Any class that contains public static void main( String[] args ) can be used to execute an application.

Answer 28

j) True

Question 29

k) The argument types in the method call need not be consistent with the types of corresponding parameters in the method’s declaration.

Answer 29

k) False. The argument types in the method call must be consistent with the types of corresponding parameters in the method’s declaration

Question 30

l) Floating-point values that appear in source code are known as floating-point literals and are type float by default.

Answer 30

l) False. Such literals are of type double by default

Question 31

Explain the public and private access modifiers in brief.

Answer 31

As the names suggest, variables or methods declared with access modifier private are accessible only to methods of the class in which they’re declared, whereas the variables or methods declared with access modifier public are “accessible to the public”—they can be accessed from methods of other classes.

Question 32

Explain the purpose of a method parameter. What is the difference between a parameter and an argument?

Answer 32

A parameter represents additional information that a method requires to perform its task. Each parameter required by a method is specified in the method’s declaration. An argument is the actual value for a method parameter. When a method is called, the argument values are passed to the corresponding parameters of the method so that it can perform its task.