Java\'s `final` vs. C \'s `const`: How Do They Differ Beyond the Surface?

Java's 'final' vs. C 's 'const': The Nuances Beyond Similarity

While the Java for C programmers tutorial suggests that Java's 'final' keyword roughly equates to C 's 'const,' a closer examination reveals subtle differences.

Function Member Semantics

In C , marking a member function 'const' signifies that it can be invoked on 'const' instances. Java lacks this feature. For instance, in C , 'i.foo()' is permitted on 'const Foo& i,' but 'i.bar()' would be prohibited.

Value Assignment

In Java, final variables can be assigned once, but later. This is not allowed in C . For example, in Java, 'a = 10;' is legal in 'public class Foo { void bar() { final int a; } }.' However, in C , such assignment would be invalid.

Member Variables

Both Java and C allow member variables to be 'final' or 'const,' respectively. In Java, these variables must be set before the constructor completes, while in C , initialization lists must be used.

Override Prevention

Java's 'final' keyword can be used to prevent method overriding. C (pre-C 11) lacks this capability. In Java, 'public final void foo() {}' in the base class cannot be overridden in derived classes. However, in C (pre-C 11), overriding would be possible.

C 11 Update

C 11 introduced 'final' to provide semantics equivalent to Java's final. This allows marking classes and member functions as 'final,' preventing overriding. Additionally, 'final' can be combined with 'const' for member functions.

Conclusion

While Java's 'final' and C 's 'const' share similarities, subtle differences exist in how they apply to member function semantics, value assignment, member variables, and override prevention. C 11 expanded 'const' to include the concept of 'final,' providing greater alignment with Java in this aspect.

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