What is the difference between Double and double in Java?

Question

What is the difference between Double and double in Java? Like when declaring a double...

double decimalNumber=0.0;

OR

Double decimalNumber=0.0;

Both work, but when I tried to change a variable I declared as a "Double" to "double" it got teh pissed.

Answer 1

Double is a class while double is a primitive. In other words, Double has a bunch of methods while all you can do with double is use it in arithmetical expressions.

There are similar constructs for all the other primitive types too.

Answer 2

As fishywiki said, double is a primitive and Double is a class.

I see that in fact you are using at least Java 5. In the code:

Double decimalNumber=0.0;

you are creating (with "autoboxing") an object. If you were using Java 1.4, you had to write:

Double decimalNumber=new Double(0.0);