Java Exceptions

An Exception is an event (problem) that occurs during the execution of a program that disrupts the normal flow of instructions. Java provides a powerful mechanism to handle these runtime errors so that the normal flow of the application can be maintained.

The Hierarchy

All exception types are subclasses of the class Throwable.

• Error: Serious problems that a reasonable application should not try to catch (e.g., OutOfMemoryError).
• Exception: Conditions that a reasonable application might want to catch.

Types of Exceptions

There are mainly two types of exceptions:

1. Checked Exceptions

Exceptions that are checked at compile-time. If some code within a method throws a checked exception, then the method must either handle the exception or it must specify the exception using throws keyword.

• Examples: IOException, SQLException.

2. Unchecked Exceptions (Runtime Exceptions)

Exceptions that are not checked at compile-time. They usually occur due to programming errors.

• Examples: NullPointerException, ArrayIndexOutOfBoundsException, ArithmeticException.

Summary