Problem with 2D Doubles array

Programming Questions

victor.hc

Problem with 2D Doubles array

in Programming Questions • 3 months ago

I want to initialize a 2D array like so:

Double[][] positions = { { -175, 0, 167.5 }, { -242.5, 0, 35 }, { 175, 0, 167.5 }, { 242.5, 0, 35 }, { 0, 0, -167.5 }, { 0, 0, -97.5 } };

but I get this error:

"cannot convert from int to Double"

anyone have an idea how I can fix this?

Thank you

Replies(3)

benj.n.su..

Re: Problem with 2D Doubles array

3 months ago

your code works for me if I change Double with a capital D to double with a lowercase d.

I know there's a difference between the two but I don't know enough to know if you actually need Double with a capital D

datguy

Re: Problem with 2D Doubles array

3 months ago

double is a primitive type, Double takes that primitive value and wraps it in an object:

http://docs.oracle.com/javase/6/docs/api/java/lang/Double.html

Java can do some automatic conversion, but apparently it has limits. It can convert the int and float literals in your example to double, and it can convert double to Double, but it refuses to do both at once. Either of the following will work:

double[][] positions = { { -175, 0, 167.5 }, { -242.5, 0, 35 } };
Double[][] positions2 = { { -175d, 0d, 167.5d }, { -242.5d, 0d, 35d } };

GoToLoop

Re: Problem with 2D Doubles array

3 months ago

Some more tips:

Processing's own pre-compiler suffixes every fractional number w/ an f. Effectively forcing them to become of data-type float. In regular Java, data-type double is the default for fractional values instead.
If you don't need any of the advanced resources from primitive-wrapped classes like Double, always uses the real primitive forms. Since they are faster, uses less memory and are more compatible w/ Processing's API!