CHAPTER 5 EXCEPTION HANDLING

Programming in C++

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Learning Outcome

At the end of this slide, student able to:

 

  Identify the different types of error in your program Understand the different types of error handler clauses? Describe the usefulness of catch and finally statement in handling

exception? Understand the rethrowing exceptions

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Exception-Handling Overview

What do you think if 4 divided by 0?

Exception-Handling Overview

It is possible C++ can calculate this equation?

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Exception-Handling Overview

C++ cannot calculate that equation, the output will be failed!!

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Exception Overview#include <iostream>

using namespace std;

const int DefaultSize = 10;

int main()

{

int top = 90;

int bottom = 0;

try

{

cout << "top / 2 = " << (top/ 2) << endl;

cout << "top divided by bottom = ";

if ( bottom == 0 )

throw "Division by zero!";

cout << (top / bottom) << endl;

cout << "top / 3 = " << (top/ 3) << endl;

}

catch( const char * ex )

{

cout << "\n*** " << ex << " ***" << endl;

}

cout << "Done." << endl;

return 0;

}

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#include <iostream> using namespace std;

const int DefaultSize = 10;

int main(){ int top = 90; int bottom = 0;cout << "top / 2 = " << (top/ 2) << endl;

cout << "top divided by bottom = "; if ( bottom == 0 ){

cout << (top / bottom) << endl;// cout << "\n*** Division by zero! ***" << endl;}

else { cout << (top / bottom) << endl;

cout << "top / 3 = " << (top/ 3) << endl; }

cout << "Done." << endl; return 0;}

Example of Exception

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Exception Description

ArithmeticException Arithmetic error, such as divide-by-zero.

ArrayIndexOutOfBoundsException Array index is out-of-bounds.

ArrayStoreException Assignment to an array element of an incompatible type.

ClassCastException Invalid cast.

IllegalArgumentException Illegal argument used to invoke a method.

IllegalMonitorStateException Illegal monitor operation, such as waiting on an unlocked thread.

IllegalStateException Environment or application is in incorrect state.

IllegalThreadStateException Requested operation not compatible with current thread state.

IndexOutOfBoundsException Some type of index is out-of-bounds.

NegativeArraySizeException Array created with a negative size.

NullPointerException Invalid use of a null reference.

NumberFormatException Invalid conversion of a string to a numeric format.

SecurityException Attempt to violate security.

StringIndexOutOfBounds Attempt to index outside the bounds of a string.

UnsupportedOperationException An unsupported operation was encountered.

Other Exception AWTException AclNotFoundException ActivationException AlreadyBoundException ApplicationException ArithmeticException ArrayIndexOutOfBoundsException AssertionException BackingStoreException BadAttributeValueExpException BadBinaryOpValueExpException BadLocationException BadStringOperationException BatchUpdateException BrokenBarrierException CertificateException ChangedCharSetException CharConversionException CharacterCodingException ClassCastException ClassNotFoundException CloneNotSupportedException ClosedChannelException ConcurrentModificationException DataFormatException

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• DatatypeConfigurationException• DestroyFailedException• EOFException• Exception• ExecutionException• ExpandVetoException• FileLockInterruptionException• FileNotFoundException• FishFaceException• FontFormatException• GSSException• GeneralSecurityException• IIOException• IOException• IllegalAccessException• IllegalArgumentException• IllegalClassFormatException• IllegalStateException• IndexOutOfBoundsException • InputMismatchException• InstantiationException• InterruptedException• InterruptedIOException• IntrospectionException• InvalidApplicationException• InvalidMidiDataException• InvalidPreferencesFormatException• InvalidTargetObjectTypeException

InvocationTargetException JAXBException JMException KeySelectorException LastOwnerException LineUnavailableException MalformedURLException MarshalException MidiUnavailableException MimeTypeParseException NamingException NegativeArraySizeException NoSuchElementException NoSuchFieldException NoSuchMethodException NoninvertibleTransformException NotBoundException NotOwnerException NullPointerException NumberFormatException ObjectStreamException ParseException ParserConfigurationException PrintException PrinterException PrivilegedActionException PropertyVetoException

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• ProtocolException• RefreshFailedException• RemarshalException• RemoteException• RuntimeException• SAXException• SOAPException• SQLException• SQLWarning• SSLException• ScriptException• ServerNotActiveException• SocketException• SyncFailedException• TimeoutException• TooManyListenersException• TransformException• TransformerException• URIReferenceException• URISyntaxException• UTFDataFormatException• UnknownHostException• UnknownServiceException• UnmodifiableClassException• UnsupportedAudioFileException• UnsupportedCallbackException• UnsupportedEncodingException• UnsupportedFlavorException• UnsupportedLookAndFeelException• UnsupportedOperationException• UserException• XAException• XMLParseException• XMLSignatureException• XMLStreamException• XPathException• ZipException

Friendly Advice about Exception

Actually, it is very difficult to remember all exception especially to junior programmer. However, the programmer can use online recourses.

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System Errors

LinkageError

Error

Throwable

ClassNotFoundException

VirtualMachineError

IOException

Exception

RuntimeException

Object

ArithmeticException

NullPointerException

IndexOutOfBoundsException

Many more classes

Many more classes

Many more classes

IllegalArgumentException

System errors are thrown by JVM and represented in the Error class. The Error class describes internal system errors. Such errors rarely occur. If one does, there is little you can do beyond notifying the user and trying to terminate the program gracefully.

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Exceptions

LinkageError

Error

Throwable

ClassNotFoundException

VirtualMachineError

IOException

Exception

RuntimeException

Object

ArithmeticException

NullPointerException

IndexOutOfBoundsException

Many more classes

Many more classes

Many more classes

IllegalArgumentException

Exception describes errors caused by your program and external circumstances. These errors can be caught and handled by your program.

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Runtime Exceptions

LinkageError

Error

Throwable

ClassNotFoundException

VirtualMachineError

IOException

Exception

RuntimeException

Object

ArithmeticException

NullPointerException

IndexOutOfBoundsException

Many more classes

Many more classes

Many more classes

IllegalArgumentException

RuntimeException is caused by programming errors, such as bad casting, accessing an out-of-bounds array, and numeric errors.

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Throwing Exceptions Example

/** Set a new radius */ public void setRadius(double newRadius) throws IllegalArgumentException { if (newRadius >= 0) radius = newRadius; else throw new IllegalArgumentException( "Radius cannot be negative"); }

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Catching Exceptionstry { statements; // Statements that may throw exceptions}catch (Exception1 exVar1) { handler for exception1;}catch (Exception2 exVar2) { handler for exception2;}...catch (ExceptionN exVar3) { handler for exceptionN;}

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Catching Exceptions

main method { ... try { ... invoke method1; statement1; } catch (Exception1 ex1) { Process ex1; } statement2; }

method1 { ... try { ... invoke method2; statement3; } catch (Exception2 ex2) { Process ex2; } statement4; }

method2 { ... try { ... invoke method3; statement5; } catch (Exception3 ex3) { Process ex3; } statement6; }

An exception is thrown in method3

Call Stack

main method main method

method1

main method

method1

main method

method1

method2 method2

method3

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Trace a Program Executionanimation

try { statements;}catch(TheException ex) { handling ex; }finally { finalStatements; }

Next statement;

Suppose no exceptions in the statements

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Trace a Program Executionanimation

try { statements;}catch(TheException ex) { handling ex; }finally { finalStatements; }

Next statement;

The final block is always executed

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Trace a Program Executionanimation

try { statements;}catch(TheException ex) { handling ex; }finally { finalStatements; }

Next statement;

Next statement in the method is executed

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Trace a Program Executionanimation

try { statement1; statement2; statement3;}catch(Exception1 ex) { handling ex; }finally { finalStatements; }

Next statement;

Suppose an exception of type Exception1 is thrown in statement2

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Trace a Program Executionanimation

try { statement1; statement2; statement3;}catch(Exception1 ex) { handling ex; }finally { finalStatements; }

Next statement;

The exception is handled.

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Trace a Program Executionanimation

try { statement1; statement2; statement3;}catch(Exception1 ex) { handling ex; }finally { finalStatements; }

Next statement;

The final block is always executed.

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Trace a Program Executionanimation

try { statement1; statement2; statement3;}catch(Exception1 ex) { handling ex; }finally { finalStatements; }

Next statement;

The next statement in the method is now executed.

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Trace a Program Executionanimation

try { statement1; statement2; statement3;}catch(Exception1 ex) { handling ex; }catch(Exception2 ex) { handling ex; throw ex;}finally { finalStatements; }

Next statement;

statement2 throws an exception of type Exception2.

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Trace a Program Executionanimation

try { statement1; statement2; statement3;}catch(Exception1 ex) { handling ex; }catch(Exception2 ex) { handling ex; throw ex;}finally { finalStatements; }

Next statement;

Handling exception

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Trace a Program Executionanimation

try { statement1; statement2; statement3;}catch(Exception1 ex) { handling ex; }catch(Exception2 ex) { handling ex; throw ex;}finally { finalStatements; }

Next statement;

Execute the final block

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Trace a Program Executionanimation

try { statement1; statement2; statement3;}catch(Exception1 ex) { handling ex; }catch(Exception2 ex) { handling ex; throw ex;}finally { finalStatements; }

Next statement;

Rethrow the exception and control is transferred to the caller