Exception Handling in Java

The exception handling is one of the powerful mechanism provided in java. It provides the mechanism to handle the runtime errors so that normal flow of the application can be maintained.

In this page, we will know about exception, its type and the difference between checked and unchecked exceptions.


  • Dictionary Meaning:Exception is an abnormal condition.
  • In java, exception is an event that disrupts the normal flow of the program. It is an object which is thrown at runtime.

Exception Handling

Exception Handling is a mechanism to handle runtime errors.

Advantage of Exception Handling

The core advantage of exception handling is that normal flow of the application is maintained. Exception normally disrupts the normal flow of the application that is why we use exception handling. Let's take a scenario:
Suppose there is 10 statements in your program and there occurs an exception at statement 5, rest of the code will not be executed i.e. statement 6 to 10 will not run. If we perform exception handling, rest of the exception will be executed. That is why we use exception handling.

Do You Know ?
  • What is the difference between checked and unchecked exceptions ?
  • What happens behind the code int data=50/0; ?
  • Why use multiple catch block ?
  • Is there any possibility when finally block is not executed ?
  • What is exception propagation ?
  • What is the difference between throw and throws keyword ?
  • What are the 4 rules for using exception handling with method overriding ?

Hierarchy of Exception classes

hierarchy of exception handling

Types of Exception:

There are mainly two types of exceptions: checked and unchecked where error is considered as unchecked exception. The sun microsystem says there are three types of exceptions:
  1. Checked Exception
  2. Unchecked Exception
  3. Error

What is the difference between checked and unchecked exceptions ?

1)Checked Exception

The classes that extend Throwable class except RuntimeException and Error are known as checked exceptions e.g.IOException, SQLException etc. Checked exceptions are checked at compile-time.

2)Unchecked Exception

The classes that extend RuntimeException are known as unchecked exceptions e.g. ArithmeticException, NullPointerException, ArrayIndexOutOfBoundsException etc. Unchecked exceptions are not checked at compile-time rather they are checked at runtime.


Error is irrecoverable e.g. OutOfMemoryError, VirtualMachineError, AssertionError etc.

Common scenarios of Exception Handling where exceptions may occur

There are given some scenarios where unchecked exceptions can occur. They are as follows:

1) Scenario where ArithmeticException occurs

If we divide any number by zero, there occurs an ArithmeticException.

2) Scenario where NullPointerException occurs

If we have null value in any variable, performing any operation by the variable occurs an NullPointerException.

3) Scenario where NumberFormatException occurs

The wrong formatting of any value, may occur NumberFormatException. Suppose I have a string variable that have characters, converting this variable into digit will occur NumberFormatException.

4) Scenario where ArrayIndexOutOfBoundsException occurs

If you are inserting any value in the wrong index, it would result ArrayIndexOutOfBoundsException as shown below:
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