Chapter 3 PDF

Question 1

What is the function of class

Answer 1

Classes combine data and the methods (code) to manipulate the data. Classes are a template used to create specific objects

Question 2

What is a requirement for all java programs in relation to classes

Answer 2

All java programs consists of at least one class

Question 3

What are the two types of classes

Answer 3

Application classes and

Service classes

Question 4

Why are classes used

Answer 4

Classes allow us to separate the data for each object, while using common code to manipulate each object

Question 5

Describe the data for a student class (example)

Answer 5

name, year, grade point average

Question 6

Describe the methods for a student class (example)

Answer 6

store/get the value of the data, promote to next year etc

Question 7

What is an object reference

Answer 7

An identifier of the object

Question 8

How do you instantiating an object

Answer 8

Creating an object of a class; assigns initial values to the object data

Question 9

What is the requirement for objects before being used

Answer 9

Objects need to be instantiated before being used

Question 10

What is the instance of a class

Answer 10

An object after instantiation

Question 11

What is the member of a class

Answer 11

The classes fields and methods

Question 12

What are two types of fields

Answer 12

instance variables and static variables

Question 13

What is an instance variable

Answer 13

Variables defined in the class and given a value in each object

Question 14

What can fields be

Answer 14

Any primitive data type and objects of the same or another class

Question 15

What are methods

Answer 15

Code to manipulate object data

Question 16

What occurs when you declare an instance variable to be private

Answer 16

They cannot be accessed directly outside of the class. Can only reference the private data of an object by calling methods of the class

Question 17

What is function of methods in relation to data

Answer 17

It encapsulates the data and provides a protective shell around it

Question 18

What is the benefit to methods

Answer 18

The classes methods can ensure that the object data is always valid

Question 19

What is the naming convention for class names

Answer 19

Start with a capital letter

Question 20

What is the naming convention for object references

Answer 20

Start with a lowercase letter

Question 21

What is the benefit of reusing code

Answer 21

Class code is already written and tested. New applications can be built faster. The applications will be more reliable

Question 22

What is the purpose of API

Answer 22

Application programming interface

Question 23

What information does the API tell us

Answer 23

How to create objects
What methods are available
How to call the methods

Question 24

What does the object reference do

Answer 24

The object reference holds the address of the object

Question 25

What is a constructor

Answer 25

A special method that creates an object and assigns initial value to data

Question 26

What is required for the constructor (in relation to the class)

Answer 26

The constructor has the same name as the class

Question 27

What is an arg list

Answer 27

The argument list is a comma separated list of initial values to assign to the object data

Question 28

What are accessor methods used for

Answer 28

Return the current values of object data

Question 29

What are mutator methods used for

Answer 29

Change the values of object data

Question 30

Describe Method Return Values

Answer 30

Can be a primitive data type, class type or void

Question 31

What is value-returning methods

Answer 31

The method returns a value Thus the method call is used in an expression When the expression is evaluated, the return value

Question 32

Describe methods with a void return type

Answer 32

Do not return a value | Method call is a complete statement

Question 33

What is the definition of argument

Answer 33

Any expression that evaluates to the specific data type

Question 34

What is a common error made with methods

Answer 34

When calling a method, include only expressions in your argument list. If you include data types in the argument list you will cause a compiler error.

Question 35

What is an object references

Answer 35

An object reference point to the memory location of object data. An object can have multiple object references pointing to it

Question 36

What occurs if an object has no object references pointing to it

Answer 36

The garbage collector will go and free the objects memory

Question 37

What is a null object reference

Answer 37

If an object reference points to no object then the value is null

Question 38

What is the other instance when an object reference can have the value null

Answer 38

Object references can have the value null when they have been declared but have not been used to instantiate an object

Question 39

How are classes grouped

Answer 39

Into packages according to functionality

Question 40

What does the string class represent

Answer 40

A sequence of characters

Question 41

What are common errors associated with a string

Answer 41

When a negative start index or a start index past the last character of the String will create an error

Question 42

What does parsing a string generally mean

Answer 42

Parsing a string generally means using several of the String methods together

Question 43

What are the DecimalFortmat and NumberFormat class used for

Answer 43

They allow you to specific the number of digits for printing and to add dollar signs and percent signs to your output

Question 44

Whats the random class used for

Answer 44

Generates a pseudorandom number

Question 45

What is the nextInt method used for

Answer 45

The nextInt method is used to generate a random integer between 1 and 6

Question 46

What does input using the scanner class allow you to do

Answer 46

Provides methods for reading byte, short, int, long, float, double, and String data types from the java console and other sources

Question 47

What is the function of the scanner class

Answer 47

Scanner parses (separates) input into sequences of characters

Question 48

What is a character sequence generally called in code

Answer 48

a token

Question 49

How are tokens usually separated

Answer 49

By standard white space characters

Question 50

What is the function of Scanner Constructor (ex: Scanner (input stream source)

Answer 50

Creates a scanner object for reading from source

Question 51

What is the difference between the next and nextline method

Answer 51

The next method will read only one word of String input whereas the next line method reads the whole line

Question 52

What is the other name for static methods

Answer 52

Static methods are also called class methods

Question 53

Can static methods be called without instantiating an object?

Answer 53

Yes, static methods can be called without having to instantiate an object

Question 54

When you call a static method, what is the general syntax used with it

Answer 54

It is important to use the dot syntax with the class name instead of the object reference

Question 55

What does implicitly mean in the context of programming

Answer 55

It is done automatically

Question 56

What are the two static constants of the Math Class

Answer 56

PI and E

Question 57

What is the PI constant used for in the Math Class

Answer 57

Pi is the value of pi

Question 58

What is the E constant used for in the Math Class

Answer 58

E is the base of the natural logarithm

Question 59

What are the rules imposed by the math round method

Answer 59

Any fractional part

Question 60

What is the wrapper class used for

Answer 60

It wraps the value of a primitive data type into an object.

Question 61

When is the wrapper class most useful

Answer 61

The wrapper class is most useful when methods require an object argument or to convert strings to an int or a double

Question 62

What is autoboxing

Answer 62

An automatic conversion between a primitive type and a wrapper object when a primitive type is used where an object is expected.

Question 63

What is unboxing

Answer 63

An automatic conversion between a wrapper object and a primitive data type when a wrapper object is used where a primitive data type is expected

Question 64

What is the methods of the character class used for

Answer 64

The charter class includes methods to test is a single character is a digit, a letter, upper