Exceptions in Java

An exception is an event, which occurs during the execution of a program, that

disrupts the normal flow of the program.

Exception Hierarchy

Unchecked

CheckedError

Three Kinds of Exceptions

• Checked - subject to the Catch or Specify Requirement.• Application can recover from it.

• Errors - external to the app, app can’t recover from. • Hardware or system malfunction.

• Unchecked – not a subject to the Catch or Specify.• Application cannot recover from it. • Usually app bugs.

Exception is a part of API

Basic example

What’s Wrong Here ?

Basic example in Java 7

What else is in Java 7

Custom Exception

Exceptions in JUnit

Exceptions in JUnit

Best Practices

• Never swallow the exception in catch block.

• Always throw specific exception.

Best Practices

• Catch specific sub-classes.

• Include cause, otherwise stack trace will be lost.

Best Practices

• Either log the exception or throw it.

• Never return or throw from finally block.

Thank you!