How do you set a double value to a "non-value"

Question

Solution

Two obvious options:

• Use Double instead of double. You can then use null, but you've changed the memory patterns involved substantially.

• Use a "not a number" (NaN) value:

  double d = 5.5;
  System.out.println(Double.isNaN(d)); // false
  d = Double.NaN;
  System.out.println(Double.isNaN(d)); // true
  

  Note that some other operations on "normal" numbers could give you NaN values as well though (0 divided by 0 for example).