Final (Java): Difference between revisions

Revision as of 21:37, 21 February 2008

Revision as of 21:38, 21 February 2008

Line 31:

Example:

<source lang="java">

public class Sphere {

public static final double PI = 3.141592653589793; // this might as well be a constant

public class Sphere {

public final double yposradius;

public static final double PI = 3.141592653589793xpos; // this might as well be a constant

public final double radiusypos;

public final double xposzpos;

public final double ypos;

public final double zpos;

Sphere(double x, double y, double z, double r) {

radius = r;

xpos = x;

ypos = y;

zpos = z;

}

[...]

}

Sphere(double x, double y, double z, double r) {

radius = r;

xpos = x;

ypos = y;

zpos = z;

}

[...]

}

</source>

Immutability of variables has great advantages, especially in optimization. For instance, Sphere will probably have a function returning its volume; knowing that its radius is constant allows us to [[memoize]] the computed volume. If we have relatively few Spheres and we need their volumes very often, the gain might be substantial. Making the radius of a Sphere final informs developers and compilers that this sort of optimization is possible in all code that uses Spheres.