What does it mean to say a type is “boxed”?

Question

I have heard of types being referred to as \"boxed\" in some languages.

In Java, I have heard of \"autoboxing\". What is this? Is it having wrapper classes for a ty

Answer 1

Yes, boxing means taking a value type and wrapping it in a reference type. Since java introduced autoboxing you can do:

void foo(Object bar) {}
//...
    foo(1);

And java will automatically turn the int 1 into an Integer. In previous versions you'd have to do:

foo(new Integer(1));

Autoboxing is most useful in java when working with generics, since you can't use primitives with generics, so to store ints in a list, you'd have to make a List and put the ints into the list boxed.