Whats the difference between byte and Byte? [duplicate]

Question

Alright so of course, I know the differences. byte is a primitive and Byte is an object. Byte offers more functions but there is one thing I dont understand. Why would anyone create a variable using Byte? It takes a lot longer. As an example:

byte primitive:
byte mikeHawk = 5;

Byte object:
byte blackHawk = Byte.valueOf((byte)5);

I've been reading a Java book and its teaching me about the object primitives. I mean, its a lot easier to add and subtract with primitives too. Maybe I am missing something. Thanks

Answer 1

The Java language has a lot of historical baggage. In Java, everything is an object – with the exception of primitive types such as int or byte that represent C-like value types. While these primitives are generally more efficient, they have some serious restrictions:

• You can't call methods on non-objects. There is a compiler technique called “autoboxing” that transparently wraps primitives in a full object in order to allow methods to be called on them. In Java, autoboxing is performed whenever a primitive is assigned or cast to the corresponding object type, e.g. when assigned to a variable or used as a method parameter.

• Type parameters for generics must be objects due to historical Java limitations. You can't have an ArrayList<byte> but must use an ArrayList<Byte>: The type parameters exist only during compile time for the purpose of static type checking, while they are treated as an Object during run time. Other languages such as C++ or C# did not use this design and can parameterize over primitive types as well.

So, while byte is the efficient representation of a byte, the Byte wrapper class contains all the overhead necessary for methods to be called and for the value to be used as a regular object.