Final (Java): Difference between revisions

Revision as of 12:59, 6 May 2008

Revision as of 13:07, 6 May 2008

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= Final variables =

A '''final [[variable]]''' is [[Immutable object|immutable]], i. e. Itit can only be assigned to once. If the variable is a field of a class, it must be assigned to in the constructor of its class. (Note: If the variable is a reference, this means that the variable cannot be re-bound to reference another object. But the object that it references is still mutable, if it was originally mutable.)

Unlike the value of a [[constant (computer science)|constant]], the value of a final variable is not necessarily known at compile time.

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Immutability of variables has great advantages, especially in optimization. For instance, <code>Sphere</code> 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<code>Sphere</code>s and we need their volumes very often, the gain might be substantial. Making the radius of a <code>Sphere</code> <code>final</code> informs developers and compilers that this sort of optimization is possible in all code that uses Spheres<code>Sphere</code>s.

[[Category:Java programming language]]