Java Chapter 4: Constructors

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Questions and Answers

What is the purpose of the Bicycle constructor?

To sort arrays of data

To display graphical user interfaces

To perform arithmetic operations

To initialize the data members with default values (correct)

How many source files are used in the given example?

Three

One

Two (correct)

Four

What is the data type of the tagNo data member?

char

int

double

String (correct)

What is the initial value assigned to the ownerName data member?

Unknown Signup and view all the answers

What is the purpose of adding a new method to the Bicycle class?

To assign a tag number Signup and view all the answers

In which file is the Bicycle class definition stored?

Bicycle.java Signup and view all the answers

What is the purpose of the setTagNo method in the Bicycle class?

To set the tag number of the bicycle Signup and view all the answers

What is the default owner name when an Account object is created?

Unassigned Signup and view all the answers

What is the purpose of the add method in the Account class?

To add an amount to the account balance Signup and view all the answers

What does the getOwnerName method return in the Account class?

The owner's name of the account Signup and view all the answers

What is the purpose of the setInitialBalance method in the Account class?

To set the initial balance of the account Signup and view all the answers

What is the purpose of the deduct method in the Account class?

To deduct an amount from the account balance Signup and view all the answers

What is the name of the class that uses both the Bicycle and Account classes?

SecondMain Signup and view all the answers

What is the initial balance set to in the Account class?

250.00 Signup and view all the answers

What is the output of the code fragment acct.add(25.00); acct.deduct(50);?

225.00 Signup and view all the answers

What is the name of the method that adds an amount to the current balance?

add Signup and view all the answers

What is the purpose of the setOwnerName method?

To set the owner's name Signup and view all the answers

What is the purpose of a parameter in a method?

To hold the value of the passed argument Signup and view all the answers

What is the requirement for matching arguments and parameters?

The number of arguments and parameters must be the same Signup and view all the answers

What happens when an argument is passed to a method?

The value of the argument is passed into memory allocated for the parameter Signup and view all the answers

What is the restriction on the assignment of arguments to parameters?

Arguments can be assigned to parameters of a compatible data type Signup and view all the answers

What is the memory allocation process for the receiving method?

Separate memory space is allocated for the receiving method Signup and view all the answers

What happens to the literal constant in the example demo.compute(i, k, 20)?

It is passed as an argument to the method Signup and view all the answers

What happens when a class component is declared private?

Client classes cannot access it Signup and view all the answers

Why should data members be declared private?

Because they are implementation details of the class Signup and view all the answers

What is information hiding?

Hiding internal details of a class from clients Signup and view all the answers

When can constants be declared public?

When they are meant to be used directly by the outside class Signup and view all the answers

What is the effect of declaring a method private?

The method cannot be accessed from outside the class Signup and view all the answers

What is the purpose of declaring class components as public or private?

To control the accessibility of class components Signup and view all the answers

Study Notes

The Purpose of the Bicycle Constructor

The Bicycle constructor sets the initial values for the Bicycle object, including its tagNo, ownerName, and balance.

Number of Source Files

The provided code example utilizes two source files: Bicycle.java and Account.java.

`tagNo` Data Type

The tagNo data member in the Bicycle class is an int (integer).

Initial Value of `ownerName`

The initial value assigned to the ownerName data member in the Bicycle class is an empty string ("").

Purpose of Adding a New Method to the `Bicycle` Class

Adding a new method to the Bicycle class extends its functionality, allowing it to perform additional tasks.

Storage Location of the `Bicycle` Class Definition

The Bicycle class definition is stored in the Bicycle.java file.

Purpose of the `setTagNo` Method

The setTagNo method in the Bicycle class allows you to update the tagNo value of an existing Bicycle object.

Default Owner Name for `Account` Objects

When an Account object is created, the default owner name is null.

Purpose of the `add` Method in the `Account` Class

The add method in the Account class increases the balance of an Account object by the specified amount.

`getOwnerName` Method Return Value

The getOwnerName method in the Account class returns the owner name associated with the Account object.

Purpose of the `setInitialBalance` Method

The setInitialBalance method in the Account class allows you to set the initial balance of an Account object.

Purpose of the `deduct` Method

The deduct method in the Account class subtracts a specified amount from the balance of an Account object.

Class Using Both `Bicycle` and `Account` Classes

The Demo class utilizes both the Bicycle and Account classes.

Initial Balance in `Account` Class

The initial balance set for an Account object is 0.00.

Output of `acct.add(25.00); acct.deduct(50);`

The output of this code fragment will be a negative balance (-25.00) as the deduct method subtracts 50.00 from the initial balance of 0.00 after adding 25.00.

Method to Add to Current Balance

The add method is responsible for adding an amount to the current balance.

Purpose of the `setOwnerName` Method

The setOwnerName method allows you to update the owner name associated with an Account object.

Purpose of a Method Parameter

A parameter acts as a placeholder for the value that will be passed to the method when it is called.

Matching Arguments and Parameters

When calling a method, the number and data types of the arguments must match the number and data types of the parameters in the method definition.

Argument Passing

When an argument is passed to a method, its value is copied to the corresponding parameter in the method's memory space.

Argument Assignment Restriction

Arguments can be assigned to parameters only if their data types are compatible.

Memory Allocation for the Receiving Method

When a method receives arguments, it creates its own local memory space to store the parameters, along with its local variables.

Literal Constant Behavior

The literal constant '20' in the example demo.compute(i, k, 20) will be treated as an integer value and passed to the compute method during execution.

Private Class Component Declaration

Declaring a class component as private restricts its access to only within the same class.

Purpose of Private Data Members

Declaring data members private enforces encapsulation, protecting them from direct manipulation outside the class, promoting data integrity.

Information Hiding

Information hiding, a key principle of object-oriented programming, involves concealing the internal implementation details of a class, making it easier to maintain and modify the code without impacting other parts of the program.

Public Constants Declaration

Constants can be declared public because their values are fixed and cannot be changed after initialization. This allows other classes to access and use them without affecting their value.

Private Method Effect

Declaring a method private restricts its accessibility to only within the same class.

Public and Private Declaration Purpose

Declaring class components as public or private controls their accessibility, enabling controlled access and data protection, promoting code reusability and maintainability.

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Description

Learn about constructors in Java, their purpose, and how they initialize data members. Understand their role in object creation and initialization tasks.