Question

Download BankAccount.java and BankAccountTester.java starting files and drag and drop them into your eclipse project. The BankAccount class declaration in file BankAccount.java is the blueprint of a BankAccount object. Check out the design of a BankAccount class.

1. In BankAccount.java class, all of the method stubs ( methods with a header but empty bodies ) are present to help you get started. Your task is to complete the method bodies. All comments in red in the diagram above indicates what each of these methods is doing. You will find similar comments in BankAccount.java as well.

2. Next, open BankTester.java and follow instructions given as comments to test all of the BankAccount methods. The expected output is provided in BankTester.java. Please read the notes below to master concepts

BankAccount
private int acctNum //a bank account number
private string name // the name of the account owner
private double balance //current balance of an account

public BankAccount() //constructor . Initialize acctNum to 0, name to “Unknown”, balance to 0.0.
public BankAccount(int aNum, string aName, double amount); // overloaded constructor . Initialize
acctNum to aNum, name to aName and balance to amount.
public void setAcctNum(int aNum) //sets instance variable acctNumr
public void setName(string aName) //sets instance variable name.
public int getAcctNum() // returns the value of instance variable acctNum.
public string getName() //returns the value of instance variable name.
public double getBalance() //returns the value of instance variable balance.
public void deposit(double amount) //adds amount to the balance.
public void withdraw(double amount) //subtracts amount from the balance.

Notes on Object Oriented Design Features:

1. Instance variables are mostly private. BankAccount only three instance variable – name, acctNum and balance. They are all private.
2. Instance variables are also called as member variables.
3. For every instance variable, there should be an accessor method (also called a get method) defined. An accessor method’s only task is to return the value of a member variable. Example: public String getName( ).
4. For every member variable, there should be a mutator method(also called a set method) defined. A mutator method’s only task is to set the value of a member/instance variable. Example: void setName(String aName).
5. A constructor method is invoked when an object is created. A constructor’s task is to initialize all member/instance variables. It is a good practice to initialize all instance variables.
6. A constructor must have the same name as the class, it is public and has no return data type. Example: public BankAccouont( ) . Notice there is no return data type.
7. A good programmer will always implement at least one constructor – the default constructor. Example: BankAccount(). A default constructor has no parameters.
8. Method is an Object-Oriented Programming (OOP) term.

Constructor Overloading :
There are two constructors in the BankAccouont class
1. public BankAccount( ) , This is default constructor.
2. public BankAccount(int aNum, string aName, double amount), This constructor has three parameters.
This is called as constructor overloading. A class designer can overload a constructor by defining multiple constructors differing in parameter types. When an object is created (Usually in static main method) with the new operator, arguments can be passed to the constructor. The constructor with matching parameters will be called. Now we can create a BankAccount object in two different ways.
BankAccount myAcct = new BankAccount();
BankAccount yourAcct = new BankAccount(3567, “Henry” , 1000);
A reference is a variable type that refers to an object. It is also called as object reference or object reference variable. A reference may be thought of as storing the memory address of an object. Variables of any class data type (and array types) are reference variables(object reference). Here myAcct and yourAcct are references to BankAccount objects.[ myAcct and yourAcct are not the names of actual object].
Memory diagrams
BankAccount yourAcct = new BankAccount();

myAcct

BankAccount yourAcct = new BankAccount(3567, “Henry” , 1000);

yourAcct

The reference variable declaration and object creation can be done in two statements instead of just one. BankAccount myAcct ; // 1.Creates a reference myAcct of a BankAccount object
with a null inside. It means that no object exists yet. It you try to use it as this point compiler will throw a null pointer exception.

myAcct
null

acctNum
m

0
unknown name
balance
footBall
0.0

Henry

acctNum
name

3567

balance
footBall

1000.0

myAcct = new BankAccount (); // 2. The new operator creates (allocates memory) for
an object, then write the object's location memory in the reference variable.
Once the above statement executes, the object is created as shown

myAcct

Thus, reference variable and its object are separate entities in memory. As a programmer, we
do not need to know the location of the object in memory, and that is why the box next to
reference variable myAcct is usually shown empty.

/*
***********************************************************
BankTester.java
Author: 
Use BankAccount class to create and manage Henry's and Joe's
bank accounts. Complete code in this class. Use comments as
your guide. Check out the expected output at the bottom. 

************************************************************/
public class BankTester
{
        public static void main(String[] args)
        {
          
         System.out.println(" Welcome to the Bank ");
                BankAccount acct1;  // Creating a reference/pointer to BankAccount object
                            //no objects exist yet only the reference variable acct1
                BankAccount acct2;  // creating  a reference/pointer to another BankAccount object
                            //no object exist yet only the reference variable acct2

        //create BankAccount object using the default constructor refer to by acct1
        acct1 = new BankAccount();
        
        
        //create BankAccount object using constructor with parameters 
        //(overloaded constructor) refer to by acct2
        //use acctNum as 3567, name as "Henry" and balance of 10000
        
        
        
        //Display summaries (state) of both the objects
        
        
        
        //set the name of acct1 to Joe, acct number to 2345 and deposits $400
        //invoke setName, setAcctNumber and deposit methods of acct1 object
        
        
        

        
        //deposit $500 to acct1 object
        
        
        //withdraw $200 from acct2 object 
        
        
        //print acct1's new balance (use getBalance())
        
        
        
        
        //print summaries of both objects refer to by acct1 and acct2 
        //reference variables.
        
        
        
        
        }
}

/*
 * Expected output

Welcome to the Bank 

        acct1 summary: 
Name: unknown
Account Number: 0
Balance: 0.0
        acct2 Summary: 
Name: Henry
Account Number: 3567
Balance: 10000.0

        acct1 summary: 
Name: Joe
Account Number: 2345
Balance: 400.0
        acct2 Summary: 
Name: Henry
Account Number: 3567
Balance: 10000.0
The acct1 balance : 900.0

        acct1 summary: 
Name: Joe
Account Number: 2345
Balance: 900.0
        acct2 Summary: 
Name: Henry
Account Number: 3567
Balance: 9800.0


 */

//*******************************************************
//BankAccount.java
//Author:
//A bank account class with methods to deposit to, withdraw from,
//change the name on, charge a fee to, and return a string
//representation of the account.
//*******************************************************

public class BankAccount
{
        private int acctNum;
        private String name;
        private double balance;
        
/*
The BankAccount constructor. Initializing 
instance variables
*/
        public BankAccount()
        {
                balance = 0;
                name = "unknown";
                acctNum = 0;
        }
        
        /*
         ADD below The BankAccount constructor with parameters. Initializing 
        instance variables to the corresponding values
        */
        

        
        
/*
The setAcctNum method stores a value in the
acctNum variable.
@param aNum The value used to set acctNum
 */

          public void setAcctNum(int aNum)
          {
             //complete the body
                   
                 
          }

/*
The setName method stores a value in the
 name field.
@param aName The value used to set name
 */

          public void setName(String aName)
          {
              
                   //complete the body
          }
           
/*
The getAcctNum method returns the value of
BankAccount object's instance variable acctNum.
@return the value in the acctNum.
*/

           public int getAcctNum()
           {
              //correct return variable  
                   return 0;
           }

/*
The getName method returns the name of
BankAccount object's instance variable name.
@return The value in the name variable.
 */

         public String getName()
         {
              //change the return from null to the variable 
                   //it is supposed to return
                 return null;
         }

/*
The getBalance method returns a BankAccount
object's balance instance variable.
 @return The value in the balance instance variable.
 */
           
          public double getBalance()
          {
                 //change the return from 0 to the variable 
                 //it is supposed to return
             return 0;
          }

          
/*
The deposit method adds amount to the 
balance 
*/              
          public void deposit(double amount)
          {
                  
                //complete the body
          }
                
/*
The withdraw checks to see if balance is 
sufficient for withdrawal.If so, decrement 
balance by amount; if not prints message. 
 */

        public void withdraw(double amount)
        {
                  
                        //complete the body
        }
                
/*
Returns a string containing the name, account number, and balance
*/
        public String toString()
        {
                return 
                          "\tName: " + name +
                          "\n\tAccount Number: " + acctNum +
                          "\n\tBalance: " + balance;  
        }
                
                        
}

Answer 1

//Completed java code

public class BankAccount
{
    private int acctNum;
    private String name;
    private double balance;

    /*
    The BankAccount constructor. Initializing
    instance variables
    */
    public BankAccount()
    {
        balance = 0;
        name = "unknown";
        acctNum = 0;
    }

        /*
         ADD below The BankAccount constructor with parameters. Initializing
        instance variables to the corresponding values
        */

    public BankAccount(int acctNum, String name, double balance) {
        this.acctNum = acctNum;
        this.name = name;
        this.balance = balance;
    }
/*
The setAcctNum method stores a value in the
acctNum variable.
@param aNum The value used to set acctNum
 */

    public void setAcctNum(int aNum)
    {
        //complete the body
        acctNum= aNum;

    }

/*
The setName method stores a value in the
 name field.
@param aName The value used to set name
 */

    public void setName(String aName)
    {

        //complete the body
        name = aName;
    }

/*
The getAcctNum method returns the value of
BankAccount object's instance variable acctNum.
@return the value in the acctNum.
*/

    public int getAcctNum()
    {
        //correct return variable
        return acctNum;
    }

/*
The getName method returns the name of
BankAccount object's instance variable name.
@return The value in the name variable.
 */

    public String getName()
    {
        //change the return from null to the variable
        //it is supposed to return
        return name;
    }

/*
The getBalance method returns a BankAccount
object's balance instance variable.
 @return The value in the balance instance variable.
 */

    public double getBalance()
    {
        //change the return from 0 to the variable
        //it is supposed to return
        return balance;
    }


    /*
    The deposit method adds amount to the
    balance
    */
    public void deposit(double amount)
    {

        //complete the body
        balance+=amount;
    }

/*
The withdraw checks to see if balance is
sufficient for withdrawal.If so, decrement
balance by amount; if not prints message.
 */

    public void withdraw(double amount)
    {
if(amount>balance)
{
    System.out.println("No sufficient amount to withdraw.");
}
else
{
    balance-=amount;
}
        //complete the body
    }

    /*
    Returns a string containing the name, account number, and balance
    */
    public String toString()
    {
        return
                "\tName: " + name +
                        "\n\tAccount Number: " + acctNum +
                        "\n\tBalance: " + balance;
    }


}

=========================================================

public class BankTester
{
    public static void main(String[] args)
    {

        System.out.println(" Welcome to the Bank ");
        BankAccount acct1;  // Creating a reference/pointer to BankAccount object
        //no objects exist yet only the reference variable acct1
        BankAccount acct2;  // creating  a reference/pointer to another BankAccount object
        //no object exist yet only the reference variable acct2

        //create BankAccount object using the default constructor refer to by acct1
        acct1 = new BankAccount();


        //create BankAccount object using constructor with parameters
        //(overloaded constructor) refer to by acct2
        //use acctNum as 3567, name as "Henry" and balance of 10000

        acct2 = new BankAccount(3567,"Henry",10000);

        //Display summaries (state) of both the objects

        System.out.println("acct1 summary:\n"+acct1);
        System.out.println("acct2 summary:\n"+acct2);


        //set the name of acct1 to Joe, acct number to 2345 and deposits $400
        //invoke setName, setAcctNumber and deposit methods of acct1 object

        acct1.setAcctNum(2345);
        acct1.setName("Joe");
        acct1.deposit(400);
        System.out.println("acct1 summary:\n"+acct1);
        System.out.println("acct2 summary:\n"+acct2);

        //deposit $500 to acct1 object

        acct1.deposit(500);
        System.out.println("acct1 summary:\n"+acct1);
        System.out.println("acct2 summary:\n"+acct2);
        //withdraw $200 from acct2 object
        acct2.withdraw(200);

        //print acct1's new balance (use getBalance())

            System.out.println("acct1's new balance: "+acct1.getBalance());


        //print summaries of both objects refer to by acct1 and acct2
        //reference variables.
        System.out.println("acct1 summary:\n"+acct1);
        System.out.println("acct2 summary:\n"+acct2);



    }
}

==================================================

//output

//if you need any help regarding this solution ............... please leave a comment ......... thanks