OOPS

Assignment - 8

Objective

Write a program to demonstrate the use of all keywords made for exception handling.

Programming Language & Compilation

• Java

$ javac Program.java
$ java Program

Source Code

Following source code demonstrates a situation where multiple customers exist with different names & a transaction is taking place. All keywords made for exception handling i.e. try, catch, finally, throw, & throws are used.

import java.lang.System;

// Entry point of the application.
public class Program {
  public static void main(String[] args) {
    ServiceProvider provider = new ServiceProvider();
    try {
      Customer customer = provider.getCustomerFromName("Hitesh");
      System.out.println("Customer with the name Hitesh is found.");
      // Chaining `Exception`s.
      try {
        customer.withdraw(6000.0);
      } catch (NotEnoughBalance e) {
        // This exception will be thrown because available balance (`4000.0`) is less
        // than required (`6000.0`).
        System.out.println(e.getMessage());
      }
    } catch (CustomerNotFound e) {
      // Handle the exception.
      e.printStackTrace();
    } finally {
      System.out.println("Transaction Complete.");
    }
  }
}

// `Exception` thrown when there is not enough balance in customer's account.
// `extends` `Exception` class from Java.
class NotEnoughBalance extends Exception {
  public NotEnoughBalance(String message) {
    super(message);
  }
}

// `Exception` thrown when a customer with a given name is not found.
// `extends` `Exception` class from Java.
class CustomerNotFound extends Exception {
  public CustomerNotFound(String message) {
    super(message);
  }
}

// A customer class to store customer's name & balance.
//
// `withdraw` method is used to withdraw the amount from the balance.
// If there is no enough balance, then `NotEnoughBalance` is thrown.
class Customer {
  private String name;
  private double balance;

  Customer(String name, double balance) {
    this.name = name;
    this.balance = balance;
  }

  public String getName() {
    return name;
  }

  public double getBalance() {
    return balance;
  }

  // `throws` `NotEnoughBalance`.
  public void withdraw(double amount) throws NotEnoughBalance {
    if (balance < amount) {
      // `throw` `NotEnoughBalance` exception if asked amount is more than the
      // balance.
      throw new NotEnoughBalance(amount + " is more than the balance (" + balance + ")");
    }
    balance -= amount;
  }
}

// A `ServiceProvider` having various customers in `registeredCustomers`.
class ServiceProvider {
  // Hardcoding data for the demo.
  private Customer[] registeredCustomers = { new Customer("John", 1000.0), new Customer("Hitesh", 4000.0),
      new Customer("Mary", 2000.0), new Customer("Peter", 50.0) };

  // Gets registered customer with a given name.
  // `throws` `CustomerNotFound` if no customer is found with the name.
  public Customer getCustomerFromName(String name) throws CustomerNotFound {
    for (Customer customer : registeredCustomers) {
      if (customer.getName().equals(name)) {
        return customer;
      }
    }
    throw new CustomerNotFound("Customer with name " + name + " is not found");
  }
}

Output

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