Const (computer programming): Difference between revisions

Revision as of 03:17, 3 September 2005

Revision as of 01:01, 8 September 2005

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i = 4; // Error! Cannot modify a "final" object

It must be decidable by the compilers where the the variable with the <code>final</code> marker is initialized, and it must be performed only once, or the class will not compile. Unlike C++'s <code>const</code>, the Java <code>final</code> keyword only protects a variable from assignment, and does not guarentee its immutability. The keyword <code>final</code> can be given to a method definition in Java, but unlike in C++ its semantics are that the method cannot be overridden in subclasses.

It is interesting to note that whereas Java's <code>final</code> and C++'s <code>const</code> keywords have the same meaning when applied with primitive variables, their meanings diverge when applied to method definitions. Java cannot simulate C++'s <code>const</code> methods. Similarly, C++ does not have any feature equivalent to Java's <code>final</code> modifier for methods, although its effect on classes can be simulated by a clever abuse of the C++ <code>friend</code> keyword.{{ref|cleverabuse}}