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NaN values are particularly problematic because they are unordered. That is, the expression NaN == NaN always returns false (see rule NUM07-J. Do not attempt comparisons with NaN for more information).

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Code Block

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double currentBalance; // User's cash balance

void doDeposit(String userInput){
  double val = 0;
  try {
    val = Double.valueOf(userInput);
  } catch (NumberFormatException e) {
    // Handle input format error
  }

  if (Double.isInfinite(val)){
    // Handle infinity error
  }

  if (Double.isNaN(val)) {
    // Handle NaN error
  }

  if (val >= Double.MAX_VALUE - currentBalance) {
    // Handle range error
  }
  currentBalance += val;
}

Exceptions

NUM08-J-EX0: Occasionally, NaN, infinity, or -infinity may be acceptable as expected inputs to a program. In such cases, explicit checks might not be necessary. However, such programs must be prepared to handle these exceptional values gracefully and should prevent propagation of the exceptional values to other code that fails to handle exceptional values. The choice to permit input of exceptional values during ordinary operation should be explicitly documented.

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Incorrect or missing validation of floating-point input can result in miscalculations and unexpected results, possibly leading to inconsistent program behavior and denial of service.