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I have two double data elements in an object.
Sometimes they are set with a proper value and sometimes not. When the form field from which they values are received is not filled I want to set them to some value that tells me, during the rest of the code that the form fields were left empty.
I can't set the values to null as that gives an error, is there some way I can make them 'Undefined'.
PS. Not only am I not sure that this is possible, it might not also make sense. But if there is some best practice for such a situation I would be keen to hear it.
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Java primitive types (such as int , double , or float ) cannot have null values, which you must consider in choosing your result expression and host expression types.
if(value != 0) //divide by value is safe when value is not exactly zero. Otherwise when checking if a floating point value like double or float is 0, an error threshold is used to detect if the value is near 0, but not quite 0.
Two obvious options:
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).
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