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11/17/2015 1K0095*Property of STI

Exception Handling

Basic Exception Handling

try , catch, and finally 

User-Defined Exceptions

 

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11/17/2015 2K0095*Property of STI

Exception

an event that occurs during the

execution of a program that disrupts the

normal flow of instructions

Two (2) types:

oChecked exception

oUnchecked exception

 

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11/17/2015 3K0095*Property of STI

Sample ExceptionsWhen a program issues a command to

read a file from a disk but the file does

not exist there

When a program attempts to write a

data to a disk but the disk is full

When a program asks for a user input

but the user enters an invalid data type

 

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11/17/2015 4K0095*Property of STI

Sample ExceptionsWhen a program attempts to divide a

value by 0

When a program tries to access an array

with an illegal index

 

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11/17/2015 5K0095*Property of STI

Exception Handling

The process used to change the normal

flow of code execution if a specified

exception occurs

 

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11/17/2015 6K0095*Property of STI

Checked Exception

Occurs during compilation

Cannot be ignored and should be

resolved to be able to execute the

program

 

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11/17/2015 7K0095*Property of STI

Checked Exceptions

 

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11/17/2015 8K0095*Property of STI

Unchecked ExceptionOccurs during execution

Also known as runtime exception

Ignored at the time of compilation

 

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11/17/2015 9K0095*Property of STI

Unchecked Exceptions

 

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11/17/2015 10K0095*Property of STI

Unchecked Exceptions

 

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11/17/2015 11K0095*Property of STI

try Block a block of code that might throw an exception

that can be handled by a matching catch block

Format:

try

{

//statement or statements that might

generate an exception

}

 

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11/17/2015 12K0095*Property of STI

catch Block a segment of code that can handle an

exception that might be thrown by the try

block that precedes it

Format:

catch (Exception exceptionName)

{

//actions to take if exception occurs

}

 

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11/17/2015 13K0095*Property of STI

try-catch Structure

 

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11/17/2015 14K0095*Property of STI

Example

 

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11/17/2015 15K0095*Property of STI

Output

 

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11/17/2015 16K0095*Property of STI

Example

 

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11/17/2015 17K0095*Property of STI

Output

 

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11/17/2015 18K0095*Property of STI

Question: What exception type will occur? 

 

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11/17/2015 19K0095*Property of STI

Answer

 

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11/17/2015 20K0095*Property of STI

Appropriate catch Block

 

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11/17/2015 21K0095*Property of STI

Question: Will the messages be displayed when

the user enters zero as divisor? 

 

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11/17/2015 22K0095*Property of STI

No. The output will still be:

 

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11/17/2015 23K0095*Property of STI

Example

 

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11/17/2015 24K0095*Property of STI

The output will be:

 

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11/17/2015 25K0095*Property of STI

What will be the output? 

 

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11/17/2015 26K0095*Property of STI

The output will be:

 

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11/17/2015 27K0095*Property of STI

 finally contains statements which are executed

whether or not an exception is thrown

Format:

finally

{

//statement or statements that

will be executed

}

 

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11/17/2015 28K0095*Property of STI

 

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11/17/2015 29K0095*Property of STI

User-Defined Exceptions

You can create a user-defined exception by

extending the Exception class.

 

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11/17/2015 30K0095*Property of STI

CustomerAccount Class (Part 1)

 

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11/17/2015 31K0095*Property of STI

CustomerAccount Class (Part 2)

 

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11/17/2015 32K0095*Property of STI

Sample Output

 

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11/17/2015 33K0095*Property of STI

Modifying the Exception Class

(Part 1)

 

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11/17/2015 34K0095*Property of STI

Modifying the Exception Class

(Part 2)

 

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