Java Enterprise in a Nutshell, Third Edition

Constants and Literals

Literals are explicit values inserted into IDL code. Sometimes literals are used to specify a default value for interface attributes or to declare the value for a constant. Literals can be Boolean (true or false), numeric (integer, floating point, or fixed point), or character-based (a single character or a string).

Literals are most often used in IDL to initialize the value of constants . Constants are named variables that are restricted from being modified after being initialized. In IDL, a constant is declared using the syntax:

// IDL
const <type spec> <identifier> = <value>;

where < type spec > is any valid basic data type or declared interface type, < identifier > is any valid IDL identifier, and < value > is any IDL expression that evaluates to a literal value. The initialization expression can be a simple literal or it can be a complex expression combining multiple literals using logical or mathematical operators. You could declare a few useful numeric constants as follows, for example:

// IDL
const float half = 1 / 2;
const float quarter = 1 / 4;

Most of the operators present in C/C++, such as addition (+), subtraction (-), multiplication (*), and the logical and bitwise operators (|, &, ^, ||, &&, etc.) are supported by IDL.

Mapping Constants to Java

If an IDL constant is declared within an interface definition, then the constant is mapped to a public static final static member on the corresponding Java interface.

If the IDL constant is declared outside of ...