SWIG:Examples:java:constants SWIG/Examples/java/constants/

Wrapping C Constants

When SWIG encounters C preprocessor macros and C declarations that look like constants, it creates Java constant with an identical value. Click here to see a SWIG interface with some constant declarations in it.

Accessing Constants from Java

Click here for the section on constants in the SWIG and Java documentation.

Click here to see a Java program that prints out the values of the constants contained in the above file.

Key points

The values of preprocessor macros are converted into Java constants.
Types are inferred by syntax (e.g., "3" is an integer and "3.5" is a float).
Character constants such as 'x' are converted into Java strings.
C string literals such as "Hello World" are converted into Java strings.
Macros that are not fully defined are simply ignored. For example:
```
#define EXTERN extern
```
is ignored because SWIG has no idea what type of variable this would be.
Expressions are allowed provided that all of their components are defined. Otherwise, the constant is ignored.
Certain C declarations involving 'const' are also turned into Java constants.
The constants that appear in a SWIG interface file do not have to appear in any sort of matching C source file since the creation of a constant does not require linkage to a stored value (i.e., a value held in a C global variable or memory location).