Types of exceptions

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Types of Exceptions

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Objectives
On completion of this period, you would be able to
learn:
•Exception hierarchy
•Types of exceptions

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Recap
•In the last class, you have studied about the concept
of multi-catch statements
•We have also written a sample program using multi
catch statements
•A program on finally block was also examined

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Exception Hierarchy
The following diagram shows exception hierarchy
Throwable
Error Exception
RuntimeException
Examples
(Out of memory error
Stack overflow errors)
Examples (ArithmeticException,
NullpointerException,
IndexOutofBoundsException)
Fig. 46.1 Exception hierarchy

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Exception Hierarchy Contd ..
•All exception types are subclasses of the built-in
class Throwable
•Throwable is at the top of the exception class
hierarchy as shown in the Fig 46.1
•Below Throwable are two subclasses that
partition exceptions into two distinct branches,
namely
•Exception
•Error

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Exception Hierarchy Contd ..
•Exception class is used for exceptional conditions
that user programs should catch
•It is used to create your own custom exception types
•RuntimeException is a subclass of Exception
•It is automatically defined for the programs that you
write
•Includes things such as division by zero and invalid
array indexing

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Error
•It defines exceptions that are not expected to be
caught under normal circumstances by your
program
•Stack overflow is an example of such an error

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Type of Exceptions
•There are two types of exceptions in Java
•Unchecked exceptions
•Checked exceptions
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Unchecked Exceptions
•The compiler does not check to see if a method
handles or throws these exceptions
•Hence the name unchecked
•They need not be included in any method’s throws
list

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Checked Exceptions
•The compiler checks whether these exceptions were
handled in the method
•That must be included in a method’s throws list
•Compiler error occurs if these exceptions were not
handled by the methods

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Unchecked Exceptions Examples
Table 46.1 Unchecked Exception

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Checked Exceptions Examples
Table 46.2 Checked Exception

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Summary
•All exception types are subclasses of the built-in
class Throwable
•Throwable is at the top of the exception class
hierarchy
•Exception, Error are subclasses of Throwable
•Types of exception
•Unchecked exceptions
•Checked exceptions

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Quiz
1.Which exceptions types are not expected to be
caught under normal circumstances by your
program
A.Error
B.Exceptions
C.None

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Frequently Asked Questions
1.Explain about the various types of Exceptions
2.List out the various checked and unchecked
exceptions