What happens if the handlers for the most specific exceptions is placed above the more general exceptions handler?

Compilation fails. The catch block for handling the most specific exceptions must always be placed above the catch block written to handle the more general exceptions.
e.g. The code below will not compile.

1 try {
// code that can throw IOException or its subtypes
} catch (IOException e) {
// handles IOExceptions and its subtypes
} catch (FileNotFoundException ex) {
// handle FileNotFoundException only
}

The code below will compile successfully :-

try {
// code that can throw IOException or its subtypes
} catch (FileNotFoundException ex) {
// handles IOExceptions and its subtypes
} catch (IOException e){
// handle FileNotFoundException only
}