Question

I have a bunch of numeric values. They can be Short, Integer, Long, Float or Double (and are the output of an external library (snakeYaml) which returns these as type Object)

I’d like to convert these Objects (which are guaranteed to be Numbers) to Double values in my program. (Storage space is not an issue).

The Java compiler obviously throws a ClassCastException when attempting to cast from an object which is actually an Short/Integer/Long/Float to a Double.

Any hints as to the most efficient method to adopt would be gratefully acknowledged.

Answer 1

They can be Short, Integer, Long, Float or Double

These classes are all subclasses of the Number class, which means that you can always use the Number.doubleValue method.

Example:

Number[] nums = { new Double(1.2), new Integer(5), new Float(3.0) };

double num1 = nums[0].doubleValue();
double num2 = nums[1].doubleValue();
double num3 = nums[2].doubleValue();

or, if you really want Double values, you can rely on autoboxing and simply do:

Double num1 = nums[0].doubleValue();
Double num2 = nums[1].doubleValue();
Double num3 = nums[2].doubleValue();