In Java, a double is a type, not a quantity of beer. Don't worry, it's not as confusing as it sounds.
It's a primitive data type, which means it takes up less memory than a byte or an int. But don't let that fool you, it's still useful for storing very, very big numbers.
Think of it like a money bin in your kitchen. You can store a lot of money in it, but it's not as exciting as arrays or lists!
So there you have it, double is a thing in Java. It's not as scary as it seems, but don't say we didn't warn you.
Why is Java so Last Century? (A rant about the good old days of Java)
Doubles are like Unicorns (A treatise on the mythical nature of double values)
What the Heck is a List? (A primer on the wondrous world of arrays)