Java User-Defined Exception

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In Java, you can create your own exception which is called user-defined exception (or) custom exception.

 

While writing your own exception classes you should remember the following points.

 

  • All exceptions should be a child of Throwable.
  • When you're going to write a checked exception, then you need to extend the Exception class.
  • When you're going to write a runtime exception, then you need to extend the RuntimeException class.

Syntax:

 class MyException extends Exception {
}

Example

File Name: InsufficientStocksException.java

import java.io.*;
// User-defined exception
public class InsufficientStocksException extends Exception {
   private double amount;
   public InsufficientStocksException(double amount) {
      this.amount = amount;
   }
   public double getAmount() {
      return amount;
   }
}

File Name: CheckingStock.java

 import java.io.*;

public class CheckingStock {
   private double balance;
   public void StockIn(double amount) {
      balance += amount;
   }
   public void StockOut(double amount) throws InsufficientStocksException {
      if(amount <= balance) {
         balance -= amount;
      }else {
         double needs = amount - balance;
         throw new InsufficientStocksException(needs);
      }
   }
}

File Name: Retailshop.java

 public class Retailshop {
   public static void main(String [] args) {
      CheckingStock cs = new CheckingStock();
      System.out.println("Stock available is 100");
      cs.StockIn(100);
      try {
         System.out.println("\n Stock Out is 200");
         cs.StockOut(200);
      } catch (InsufficientStocksException e) {
         System.out.println("Sorry, there is Insufficient Stocks is" + e.getAmount());
         e.printStackTrace();
      }
   }
}

Output

Stock available is 100
Stock Out is 200
Sorry, there is Insufficient Stocks is 100
InsufficientStocksException
         at CheckingStock.StockOut(CheckingStock.java:8)
         at Retailshop.main(Retailshop.java:10)
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