Advance Object Oriented Programming.

In this example we will see Advance Object Oriented Programming.

We will use a simple banking example for this.

Steps:

1. Create folder “src”. This will contain all java files.
2. Then create AdvOOPTest1 to test the application.

The structure will be as follow

• src/InsufficientFundsException.java
• src/IllegalTransferException.java
• src/Account.java
• src/CustomerAccount.java
• src/CurrentAccount.java
• src/SavingsAccount.java
• src/Banker.java
• AdvOOPTest1.java

IllegalTransferException.java

package com.pravin.banking;




public class IllegalTransferException extends RuntimeException{}

Account.java

package com.pravin.banking;




/**

An abstract super-class for all account types in the bank.

@author Pravin

@see SavingsAccount

@see CurrentAccount

*/

public abstract class Account{

long id;




/**

Returns ID of this account.

*/

public long getId(){

return id;

}




/**

Returns the current-balance in this account.

*/

public abstract double getBalance();




/**

Credits the specified amount in this account.

*/

public abstract void deposit(double amount);




/**

Debits the specified amount from this account.

@throws InsufficientFundsException Specified amount cannot be withdrawn

*/

public abstract void withdraw(double amount) throws InsufficientFundsException;




/**

Transfer specified amount to another account.

@param amount Funds to transfer

@param other The target account

@throws InsufficientFundsException This account does not hold specified

amount

@throws IllegalTransferException Target account is identical to this

account

*/

public final void transfer(double amount, Account other)

throws InsufficientFundsException{

if(other == this)

throw new IllegalTransferException();

this.withdraw(amount);

other.deposit(amount);

}

}

CustomerAccount.java

package com.pravin.banking;




public abstract class CustomerAccount extends Account{

protected double balance;




public double getBalance(){

return balance;

}




public void deposit(double amount){

balance += amount;

}

}

CurrentAccount.java

package com.pravin.banking;




public final class CurrentAccount extends CustomerAccount{

public void withdraw(double amount){

balance -= amount;

}

}

SavingsAccount.java

package com.pravin.banking;




public final class SavingsAccount extends CustomerAccount

implements Profitable{

public static final double MIN_BALANCE = 500.0;




public SavingsAccount(){

balance = MIN_BALANCE;

}




public void withdraw(double amount) throws InsufficientFundsException{

if(balance - amount <>

throw new InsufficientFundsException();

balance -= amount;

}

public double addInterest(int period){

float rate = (balance <>

double interest = balance * rate * period / 100;

balance += interest;

return interest;

}

}

Banker.java

package com.pravin.banking;




public class Banker{

private static Banker singleton;




private long nextId;




private Banker(){

nextId = System.currentTimeMillis() % 1000000;

}




public static Banker getBanker(){

if(singleton == null)

singleton = new Banker();

return singleton;

}




public Account openAccount(double amount, boolean savings){

Account acc;

if(savings)

acc = new SavingsAccount();

else

acc = new CurrentAccount();

acc.id = nextId++;

acc.deposit(amount);

return acc;

}




public final Account openAccount(double amount){

return openAccount(amount, false);

}

}

AdvOOPTest1.java

import com.pravin.banking.*;




class AdvOOPTest1{

public static void main(String[] args){

Banker b = Banker.getBanker();

Account cust = b.openAccount(4500, true);

Account vend = b.openAccount(0);

try{

double amt = Double.parseDouble(args[0]);

cust.transfer(amt, vend);

}catch(InsufficientFundsException e){

System.out.println("ERROR: Transfer aborted due to lack of funds!");

}catch(Exception e){

System.out.printf("ERROR: %s%n", e);

}

System.out.printf("Customer Account ID is %d and Balance is %.2f%n", cust.getId(), cust.getBalance());

System.out.printf("Vendor Account ID is %d and Balance is %.2f%n", vend.getId(), vend.getBalance());

}

}

To compile:

javac -d . src/*.java

javac AdvOOPTest1.java

To run:

java AdvOOPTest1 2000