JAVA primitive data types - Signed/ unsigned etc.

1. Are the following data types signed or unsigned in JAVA?
byte, short, int, long, float, double
2. I have tried using "Integer" in place of "int" and the program runs perfectly. Why is this so when "Integer" is not a reserved word in JAVA?
Thanks.

And to answer your first question, byte, short, int, long, float and double are all signed.
As a part of the core of the language, Sun developed a series of 'collections' classes; Vector, ArrayList, etc. All of these classes, in the days before generics, were able to store instances of the Object class or anything that derived from it. Therefore, to store an int, a float or a double value into one of these collections classes, it was necessary to wrap it up in an instance of one of those classes that derived from Number. These are the wrapper classes that the previous poster alluded to. Typically, the wrapper class has a similar name to the primitive data type but with a capital latter; int - Integer, double - Double, etc.

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