What pitfalls come from comparing floating-point or wrapper values in loop conditions and switch?

Floating-point loop counters accumulate rounding error, so 'for (double d = 0; d != 1.0; d += 0.1)' may never terminate — always count with an int or compare with a tolerance. switch on a boxed Integer auto-unboxes and throws NullPointerException if the value is null, which a bare null check before the switch would have caught. These are the kinds of edge cases that pass unit tests with round numbers but fail in production data.