lec15 - CS240 Programming in C Lecture 15 Exception...

CS240: Programming in C
Lecture 15: Exception Handling
Monday, April 4, 2011

Exceptions

An exception is a control-flow mechanism that
allows unexpected (and perhaps erroneous)
conditions to be caught and handled

Key property: the handler for an exception
need not be lexically apparent at the point
where the exception is raised

Concept: lexical vs. dynamic scope
2
Monday, April 4, 2011

The Call Stack
3
Suppose function f calls function g which then calls function
h
f
g
h
provide a handler for
exception E
raise exception E:
control directly reverts
to the handler defined
in f
f
Monday, April 4, 2011

In Java ...
4
public void divide(int numberToDivide, int numberToDivideBy)
throws BadNumberException{
if(numberToDivideBy == 0){
throw new BadNumberException("Cannot divide by 0");
}
return numberToDivide / numberToDivideBy;
}
public void f(){
try {
int result = g(2,1);
System.out.println(result);
} catch (BadNumberException e) {
//do something clever with the exception
System.out.println(e.getMessage());
}
System.out.println("Division attempt done");
public void g(int x, y){
....