Double vs doubleValue in Java

Question

if a method returns a Double, why would we call the method "doubleValue" on it? it already returns a double and in calculations, appears to evaluate correctly.

Answer 1

Prior to Java 1.5 auto-boxing (and unboxing) didn't exist in Java. So, you would need this to extract the underlying primitive from a Double.

If you are unfamiliar with auto-boxing, you can read more here. http://docs.oracle.com/javase/1.5.0/docs/guide/language/autoboxing.html

Answer 2

You call 'doubleValue' on a Double object to convert from the boxed Object to the primitive data type. Since most of the time the Double is auto-unboxed to a double, you usually don't need to do this, but if you want to be explicit in your conversion, you can call this method.