The Java compiler type-checks the arguments to each varargs method to ensure that the arguments are of the same type or object reference. However, the compile-time checking is ineffective when Object or generic T parameter types are used [Bloch 2008]. Another (Note that it does not matter if there are initial parameters of specific types, the compiler will still not be able to check Object or generic T vararg parameter types.) A requirement for providing strong compile-time type checking of variable argument methods is to be as specific as possible when declaring the type of the method parameter.
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Collection<T> assembleCollection(T... args) {
Collection<T> result = new HashSet<T>();
// add each argument to the result collection
return result;
}
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DCL60-EX1: In some circumstances, it is necessary to use a vararg parameter of type Object. A good example of this is the method java.util.Formatter.format(String format, Object... args) which can format objects of any type.
Risk Assessment
Injudicious use of varargs parameter types prevents strong compile-time type checking, creates ambiguity, and diminishes code readability.
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