User-define Exception

User-defined ExceptionsYou can create your own exceptions in Java. Keep the following points in mind when writing your own exception classes:

1. All exceptions must be a child of Throwable.
2. If you want to write a checked exception that is automatically enforced by the Handle or Declare Rule, you need to extend the Exception class.
3. If you want to write a runtime exception, you need to extend the RuntimeException class.

We can define our own Exception class as below:class MyException extends Exception{}You just need to extend the predefined Exception class to create your own Exception. These are considered to be checked exceptions. The followingInsufficientFundsException class is a user-defined exception that extends the Exception class, making it a checked exception. An exception class is like any other class, containing useful fields and methods.Example:// File Name InsufficientFundsException.javaimport java.io.*;public class InsufficientFundsException extends Exception{   private double amount;   public InsufficientFundsException(double amount)   {      this.amount = amount;   }    public double getAmount()   {      return amount;   }}To demonstrate using our user-defined exception, the following CheckingAccount class contains a withdraw() method that throws an InsufficientFundsException.// File Name CheckingAccount.javaimport java.io.*;public class CheckingAccount{   private double balance;   private int number;      public CheckingAccount(int number)   {      this.number = number;   }      public void deposit(double amount)   {      balance += amount;   }      public void withdraw(double amount) throws InsufficientFundsException   {      if(amount <= balance)      {         balance -= amount;      }      else      {         double needs = amount - balance;         throw new InsufficientFundsException(needs);      }   }      public double getBalance()   {      return balance;   }      public int getNumber()   {      return number;   }}The following BankDemo program demonstrates invoking the deposit() and withdraw() methods of CheckingAccount.// File Name BankDemo.javapublic class BankDemo{   public static void main(String [] args)   {      CheckingAccount c = new CheckingAccount(101);      System.out.println("Depositing $500...");      c.deposit(500.00);            try      {         System.out.println("\nWithdrawing $100...");         c.withdraw(100.00);         System.out.println("\nWithdrawing $600...");         c.withdraw(600.00);      }catch(InsufficientFundsException e)      {         System.out.println("Sorry, but you are short $" + e.getAmount());         e.printStackTrace();      }    }}Compile all the above three files and run BankDemo, this would produce the following result:Depositing $500...Withdrawing $100...Withdrawing $600...Sorry, but you are short $200.0InsufficientFundsException        at CheckingAccount.withdraw(CheckingAccount.java:25)        at BankDemo.main