K&B Chapter 4: Assertions

[Marco Beelen]

In the section about Using Assertions Appropriately, it states the 'assert false'-statement can be used if a section of code never should be reached.
It is shown with an example of a switch-case-statement:

switch (x) {
case 2: y=3;
case 3: y=17;
case 4: y=27;
default: assert false; // We're never supposed to get here.
}

The example isn't very good IMHO, because this example would qualify to be an exam question, because based upon the fall-through this would always throw an AssertionError, due to this missing break; statements.

[Mike Gershman]

That is the point. The assertion statement quickly flags a logic error that otherwise would be harder to find.

[Adam Czysciak]

Originally posted by Marco Beelen:

switch (x) {
  case 2: y=3;
  case 3: y=17;
  case 4: y=27;
  default: assert false; // We're never supposed to get here.
}
 

The example isn't very good IMHO, because this example would qualify to be an exam question, because based upon the fall-through this would always throw an AssertionError, due to this missing break; statements.

No, this will throw AssertionError only if assertions are enabled.