Method Overloading supporting Polymorphism in Java

Question

Method Overloading supports polymorphism because it is one way that Java implements one-interface, multiple methods paradigm.

To understand how, I consider the following. In languages that do not support method overloading, each method must be given a unique name. However, frequently I will want to implement essentially
the same method for different types of data. Consider the absolute value function. In languages that do not support overloading, there are usually 3 or more versions of this function, each with a slightly different name. For instance in C, the function abs() returns the absolute value of an integer, labs() returns the absolute value of an long integer, fabs() returns the absolute value of an floating-point value. Since C does not support overloading, each function has to have its own name, even though all 3 functions do essentially the same thing. This makes the situation more complex, conceptually, than it actually is. Although the underlying concept of each function is the same, I will have 3 names to remember. This situation doesn’t occur in Java, because each absolute value method can use the same name. Indeed, Java’s standard class library includes an absolute value method, called abs(). This method is overloaded by Java’s Math class to handle all numeric types. Java determines which version of abs() to call based upon type of argument.

There is no rule stating that overload method must relate to one another. However from a stylistic point of view, method overloading implies a relationship. Thus, while I can use the same name to overload unrelated method, I think I should not. For example, I could have use the name sqr to create methods that return the square of an integer and the square root of a floating point value. But these 2 operations are fundamentally different. Applying method overloading in this manner is defeating its original purpose.

So in practice, should I only overload closely related operations? And any other reason to use overloaded methods besides this?

You should overload when you need to (i.e. when it would increase clarity to the maintainer/reader of your code). — Oliver Charlesworth
So I need to think more for method names, rather than the business logic :D — Suresh Atta
Overloading is used when you want to do the same kind of processing on different classes of data — CocoNess
In your example, you suggest using the method name sqr for both square and square root. This is not valid application for overloading, although syntactically it would work — CocoNess

blagae blagae · Accepted Answer · 2014-09-15T08:07:34

As far as I can see, method overloading is typically used only for supplying sensible default arguments to a method, in order to simplify the API. It can have some advantages when you or other users may not need all the offered flexibility available on your program/library.

Another valid use is for the primitive data types in Java, as you pointed out yourself.

void doThis() {
    doThis(true);
}

void doThis(boolean firstArg) {
    doThis(firstArg, 1);
}

void doThis(int secondArg) {
    doThis(true, secondArg);
}

// actual logic using several parameters
void doThis(boolean firstArg, int secondArg) {
    if (firstArg) {
        System.out.println(secondArg+1);
    }
    else {
        System.out.println(secondArg-1);
    }
}

Of course this is a nonsense example, but it becomes more apparent when, for example, your method requires a PrintStream. You can supply System.out as the default in an overloaded method, but your logic should be in a method where any PrintStream can be supplied. Using the same method name for radically different uses or outputs is a big no-no, it would most likely infuriate anyone working with your code (including Future You: http://xkcd.com/1421/ ).

Method Overloading supporting Polymorphism in Java

1 Answers