benifits/drawbacks of returning a const or final value/reference from any method

Question

I am a novice programmer exploring the depths of C. Why does some inbuilt functions return a const value ? Can somebody explain the benefits or drawbacks of using const in method returns ?

Answer 1

Using final and const in returning values from functions and methods is to keep people from changing their values. For example, if i had (in c)

char* getChar()
{
   return "string";
}

and I didn't want someone to use it like

char myChar = getChar()[0]++;

then i would have to return a const, to keep it from being changed.

For Java, it's very different. You don't return final values, you make methods final.

final is used with a Java method to mark that the method can't be overridden (for object scope) or hidden (for static). This allows the original developer to create functionality that he can be sure will not be changed by others, and that is all the guarantee it provides.

Answer 2

C's const and Java's final are very different, and especially in the case you're talking about.

In C (disclaimer: I haven't done C in a while so please let me know where I'm wrong) let's look at this example:

const int something() {
    return 3;
}

The const is meaningless because it's not like you can do:

something() = 3;

For some more information on const return values in C, take a look at the following:

• const makes no sense for return values...
• Purpose of returning by const value (this is C++, but still useful).

In Java, I'm assuming you're talking about something like:

public final int something() {
    ...
}

Here final has nothing to do with the return value. final here means that if you extend the class that something() belongs to, you cannot override the implementation of something(). This is somewhat similar in spirit to final variables; these are variables whose values you cannot change once they are set.