Classes and Objects - Beginning Java 8 Fundamentals - page 270

■ If a varargs method is overloaded, java uses the more specific version of the method instead of using a varargs
method. java uses varargs method as the last resort to resolve a method call.

Tip

Sometimes a call to an overloaded varargs method may cause confusion to the Java compiler. The overloading of
the method itself may be valid. However, the call to it may cause an issue. Consider the following snippet of code for
the MathUtil7 class, which is a valid example of method overloading:

public class MathUtil7 {
public static int max(int...num) {
// Code goes here
}

public static int max(double...num) {
// Code goes here
}
}

Which version of the max() method will be called when the following statement is executed?

int max = MathUtil7.max(); // Which max() to call?

The above statement will generate a compilation time error stating that the call to MathUtil7.max() is
ambiguous. Java allows you to pass zero or more values for a variable-length argument. In the above statement,
both methods max(int...num) and max(double...num) qualify for the MathUtil7.max() call. The compiler cannot
decide which one to call. You may find many other instances where a call to an overloaded varargs method results in
an ambiguous method call and the compiler will generate an error. The error message will guide you to the
offending code.

Varargs Methods and the main() Method
Recall that if you want to run a class, you need to declare a main() method in it with a String array as its argument.
The signature for the main() method must be main(String[] args) . A varargs method is implemented by Java
compiler using an array. If your method signature is m1(XXX...args) , it is changed to m1(XXX[] args) by the
compiler. Now you can declare the main() method of your class using the older notation that uses a String array or
using a newer notation that uses a varargs. The following declaration of main() method for the Test class is valid. You
will be able to run the Test class using the java command.

public class Test {
public static void main(String...args) {
System.out.println("Hello from varargs main()...");
}
}